(covers information from several alternate timelines)
Julian Bashir was born in late 2341. Originally named "Jules," he changed his name, at age 15, to "Julian." His parents were Richard and Amsha Bashir and he was an only child. (DS9: "Doctor Bashir, I Presume")
One of Julian's most prized possessions as a child was his stuffed teddy bear, Kukalaka. When Julian was a boy, he took him everywhere he went. In 2346, at the tender age of five, Bashir performed his first surgery when he re-stuffed his well-worn Kukalaka. Bashir continued to hang on to Kukalaka well into his adulthood. (DS9: "The Quickening", "In the Cards", "Inquisition")
At age six, Bashir was small, not very bright, and a bit physically awkward for his age. In the first grade, while the other children were learning how to read and write and use a computer, Julian was still trying to tell a dog from a cat and a tree from a house. (DS9: "Doctor Bashir, I Presume") He never really could understand what was happening, but he knew that he wasn't doing as well as his classmates. There were several concepts they took for granted that he couldn't begin to master, but he didn't know why. All he knew was that he was a great disappointment to his parents.
In 2348, just before Julian's seventh birthday, the Bashir family left Earth for Adigeon Prime. At first, he was excited to see all the aliens in the hospital, but then they gave him a room and started a series of treatments. These treatments, known as "accelerated critical neural pathway formation," were a method of genetic engineering that involved the resequencing of his DNA. Over the course of two months, his genetic structure was manipulated to accelerate the growth of the neuronal networks in his cerebral cortex, and a new Julian Bashir was born.
The focus of his "enhancements" were to increase his mental abilities and as such, his IQ jumped five points a day for over two weeks. Further treatments led to improvements in his hand-eye coordination, reflexes, vision, stamina, height, and weight. In the end, everything but his name had been altered in some way, which led Julian to do so himself by refusing to ever again answer to the name "Jules."
The Bashirs returned to Earth and moved to a different city, where Julian was enrolled in a new school using falsified records his parents obtained somewhere. Instead of being the slowest learner in his class, Bashir was the star pupil. (DS9: "Doctor Bashir, I Presume")
As a child, Bashir was afraid of doctors because they seemed to know everything, as if they held the power of life and death in their hands. He used to think that if he didn't behave, they would make him sick. (DS9: "Equilibrium") In 2351, at the age of ten, he was living with his family on Invernia II. He and his father got caught in an ionic storm and found shelter with a girl who became ill and later died because no one present knew that a nearby herb could have saved her. This memory further influenced Bashir's choice to become a doctor. (DS9: "Melora") As he got older, he decided that he wanted to know what doctors knew, to be as smart as they were. Upon furthering his education, he learned that all he really wanted to do was help people. (DS9: "Equilibrium")
In 2356, at the age of fifteen, Julian stopped calling himself Jules when he found out his parents had him genetically enhanced, believing that his parents had considered him defective. (DS9: "Doctor Bashir, I Presume")
Julian, however briefly, considered becoming a professional tennis player. (DS9: "Melora") Although good enough to play professionally, he decided to give it up and become a doctor instead, knowing that his parents would approve more of his career choice. (DS9: "Distant Voices")
Starfleet Medical Academy
On New Year's Eve, 2367, Bashir attended a party at the home of Bruce Lucier, with his Andorian friend, Erit – Elizabeth Lense also attended. At the party, Erit (the Andorian) was pointed out to Lense as being Bashir, causing her to have mistaken Bashir for an Andorian for four years. (DS9: "Explorers")
Bashir was the captain of the Medical Academy racquetball team. His team won the sector championships in his final year. When he played against a Vulcan rival in his final match however, he found his greatest opponents were the ones with no formal training. At another tournament, he picked up a five-thousand-year-old battle warm-up exercise from a top player. According to legend, the warm-up makes the heart a friend to the hand. (DS9: "Rivals")
Julian graduated in 2368 as salutatorian, missing one question on the final, where he mistook a preganglionic fiber for a postganglionic nerve during the oral exam phase of his Starfleet Medical finals. (DS9: "Emissary", "Q-Less", "Distant Voices") The valedictorian of his class was Elizabeth Lense. (DS9: "Explorers") Despite graduating salutatorian, he did graduate first in his class in pediatric medicine. (DS9: "To the Death")
After graduation, Bashir was offered the choice of any job in the fleet. He was also offered a position at a prestigious medical complex in Paris by its top administration, Mr. Delon, the father of Bashir's then-girlfriend, Palis Delon. He promised Bashir he would be chief of surgery within five years, which meant Bashir would have to give up his Starfleet career. Bashir came very close to taking the position but subsequently gave it up, as well as Palis. (DS9: "Armageddon Game")
Deep Space 9
Choosing to stay in Starfleet, and not wanting a cushy job or a research grant, Bashir chose an assignment aboard starbase Deep Space 9. At the time, it was one of the most remote outposts available, located beyond the farthest reaches of the Federation, allowing Bashir the chance to study "real frontier medicine". On stardate 46379, 27-year-old lieutenant junior grade Bashir was transported to his new posting at Deep Space 9 by the USS Cochrane. It did not take Bashir long to experience frontier medicine. During the first week of the Federation take-over of Deep Space 9, the station was attacked by Gul Jasad of Cardassia, who believed that the station had destroyed a Cardassian vessel. The vessel had really entered a stable wormhole near the station. Bashir was called to the station's Promenade to treat the wounded. (DS9: "Emissary")
While serving on Deep Space 9, he met Elim Garak, a Cardassian tailor, who Bashir thought might have been a spy. (DS9: "Past Prologue") Bashir was enthralled by him and they became friends, with Bashir frequently trying to pry secrets from Garak. (DS9: "Past Prologue", "Cardassians", "The Wire")
Later that year, he accompanied Benjamin Sisko, Kira Nerys, and Kai Opaka on a journey through the Gamma Quadrant. They crash landed on a moon where war was eternal, and the combatants did not die. He, along with Miles O'Brien, visited a village on Bajor and helped the people pick a new Sirah to drive off the Dal'Rok, an energy being, from the village. (DS9: "Battle Lines", "The Storyteller")
During an away mission, Bashir rescued a Kobliad security officer from a burning ship. The criminal she was transporting transferred his mind into Bashir's mind and controlled Bashir into committing criminal acts, until he was driven out of his consciousness and destroyed. (DS9: "The Passenger")
At one point, Bashir became a Human game-piece in a Wadi game that Quark was forced to play to teach him a lesson in honesty. Quark believed that if he lost, his friends would die, but it was only a game. (DS9: "Move Along Home")
He began a friendship with Elim Garak, the only Cardassian on the station. He saved his life by removing an implant from his brain that had been put there by Enabran Tain, the former head of the Obsidian Order. Together, they also exposed Gul Dukat's plot to embarrass Kotan Pa'Dar, whose son was left on Bajor during the Cardassian Withdrawal from the planet. (DS9: "The Wire", "Cardassians")
Bashir and O'Brien helped destroy the nano-biogenic weapons of the T'Lani and Kellerun. Officials of both races ordered the assassination of both men in order to make sure that the secrets of the weapons would not become known. (DS9: "Armageddon Game")
In 2370, he became the first Starfleet officer to cross over to the mirror universe in more than a hundred years. His counterpart was one of the leaders of the Terran Rebellion against the Alliance. (DS9: "Crossover")
He unknowingly took part in a fixed racquetball game against O'Brien. A swindler had opened a new bar on the station and was hurting Quark's business. Bashir was the favorite in the game, and by fixing it so O'Brien won, would have garnered Quark huge profits. (DS9: "Rivals")
In 2371, Bashir, along with Jadzia Dax and Sisko, was accidentally transported back in time. They went back three hundred years to the time of the Bell Riots on Earth. It was a time of social upheaval and they were instrumental in helping the government become aware of the poor. Later in 2371, he was attacked by Altovar, a Lethean who was attempting to steal bio-mimetic gel from the infirmary. The Lethean's telepathic attack put Bashir into a coma, but Bashir managed to fight his way back to consciousness. Shortly thereafter, he helped O'Brien expose a Romulan plot to destroy the wormhole through a series of time jumps. (DS9: "Past Tense, Part I", "Past Tense, Part II", "Distant Voices", "Visionary")
After an attack by the Jem'Hadar, the USS Defiant was heavily damaged. Bashir and Dax were trapped in a turbolift, with a limited supply of air. Just as their air ran out, they were freed from the lift. (DS9: "Starship Down")
During the war with the Klingons, Bashir saw war close up. He attended to the wounded on a colony attacked by the Klingons. With limited medical facilities, he was still able to treat and save many of the wounded. (DS9: "Nor the Battle to the Strong")
Bashir was promoted to full lieutenant in 2372. Early that year, Bashir participated in drills aboard Deep Space 9, in preparation for potential Changeling infiltrators, where he coordinated phaser sweeps of the Promenade. On stardate 49011, Bashir prepared his staff for the pending Klingon assault on the station. (DS9: "The Way of the Warrior")
On stardate 49066, Bashir and Chief O'Brien conducted a mission to the Gamma Quadrant that included a bio-survey of Merik III. En route to the Bajoran wormhole, their runabout, the Rubicon, detected a subspace magneton pulse in the Bopak system. The source was later determined to be coming from a Jem'Hadar attack ship, located on the planet Bopak III. (DS9: "Hippocratic Oath")
Later that year, Bashir was at a burn treatment conference on Meezan IV. He went to bed one night and woke up in the Dominion Internment Camp 371. Meanwhile, a Changeling had replaced the doctor aboard the station for over a month. (DS9: "In Purgatory's Shadow") The Changeling Bashir remained aboard Deep Space 9, secretly laying the pieces of a plan to trigger a supernova in the Bajoran sun with a bomb composed of trilithium, tekasite, and protomatter, in order to wipe out a large chunk of the combined Alpha Quadrant fleet at once. When the time came, the Changeling Bashir hijacked the runabout Yukon to perform his mission, but at about the same time, the real Bashir and his fellow prisoners escaped the internment camp. Bashir was able to alert the station that the other Bashir was a fake just in time, and the Changeling plot was thwarted by the Defiant. (DS9: "By Inferno's Light")
Bashir enjoyed the holosuites at Quark's. One of his favorite programs was a spy novel, with Bashir in the title role. When the explosion from a sabotaged runabout blew out the station's transporter, Michael Eddington was forced to save the patterns of Sisko, Dax, Kira, O'Brien, and Worf in the station's computer. Their neural patterns took up so much space in the main computer that it had to store their physical patterns in the holosuite Bashir was running, causing the senior staff to appear as characters in his program. (DS9: "Our Man Bashir")
Bashir's genetically engineered status was revealed in 2373, after Lewis Zimmerman chose him to be the template for the Long-term Medical Holographic program. Despite standing regulations, Starfleet opted to make an exception to its rules barring resequenced personnel, provided Bashir's father accept incarceration for violation of eugenics laws, which he did. (DS9: "Doctor Bashir, I Presume")
Bashir participated in numerous military operations during the war. He was with Sisko when they destroyed the ketracel-white storage depot. The Jem'Hadar ship they used suffered heavy damage and lost its warp drive. When the ship crashed, it was on a planet where a Jem'Hadar ship had previously crashed. A battle ensued between the crews. Elim Garak and Nog were captured by the Jem'Hadar. But with Keevan, the Vorta leader hurt, they were released in exchange for Bashir treating Keevan. Bashir operated on him and saved his life. Keevan then betrayed his forces because he had run out of ketracel-white and worried that the Jem'Hadar would kill him. (DS9: "A Time to Stand", "Rocks and Shoals")
Bashir took part in the recapturing of the station and driving the Dominion back to Cardassian space. Later that year, he was a part of Worf's and Jadzia's wedding. He and O'Brien used Ma'Stakas to attack Worf and Jadzia at the end of the wedding, which was a Klingon tradition (as well as an opportunity for the two to vent their frustrations over the trials and suffering endured during the symbolic lead-up to the wedding ceremony itself). While studying genetically-engineered Humans, he learned from them that the attempt by the Dominion to open peace talks and cede territory was a ruse in order to acquire planets that could help produce ketracel-white. (DS9: "Favor the Bold", "Sacrifice of Angels", "You Are Cordially Invited", "Statistical Probabilities")
Bashir took part in the defense of AR-558, which was a planet that guarded the supply route of the Federation. He found a cure for the virus that Section 31 infected Odo with, saving Odo's life. Bashir took part in the final battle of the war. After the war was won by the Federation Alliance, Bashir said goodbye to his friend, Miles O'Brien and began a relationship with Ezri Dax. (DS9: "The Siege of AR-558", "Extreme Measures", "What You Leave Behind")
On stardate 46578, Bashir boarded the USS Enterprise-D to access its computer's bio-imaging systems in sickbay, following the discovery of what he believed was a medical scanner discovered in the Gamma Quadrant. With the assistance of Commanders Data and La Forge, they ran a full circuit pathway diagnostic on the device in engineering. While working with Data, Bashir became interested in cybernetic research. Bashir was fascinated by all the trouble his creator took to make Data, who he referred to as a "synthetic lifeform", seem "Human". He was especially surprised by how "personable" Data was, and among other things, questioned Data about whether his hair grew, and observed that Data was "breathing" and had a "pulse", questions that Data had never been asked before, people being more focused on how he was different from Humans rather than how he was similar to them.
During their investigation of the device, it emitted a plasma shock that overloaded Data's positronic net, activating a series of previously dormant circuits that subsequently allowed Data the ability to dream. With Data's permission, Bashir took this opportunity to author a paper on the subject with the intentions of getting published in the Starfleet Cybernetics Journal. (TNG: "Birthright, Part I")
One of Bashir's notable projects was on biomolecular replication. His work was submitted by Jadzia Dax and later nominated by the Federation Medical Council for 2371's Carrington Award for his work, which was, according to Dax, "both audacious and groundbreaking." This made Bashir the youngest nominee in the history of the Carrington Award. He was honored to be nominated, but felt that the undeniable truth was that he was far too young to be a serious candidate for the award. (DS9: "Prophet Motive")
Another of Bashir's early research topics on Deep Space 9 was an immuno-therapy project of T-cell anomalies conducted on Bajor. Doctor Lense had read Bashir's research and was extremely interested in his work. (DS9: "Explorers")
While on Bopak III, Goran'Agar, a Jem'Hadar, implored Bashir to conduct some scientific research in order to find the cure for their addiction to ketracel-white. Bashir agreed, and initially tested for potential matches containing the molecular structure of the enzyme receptors in the Jem'Hadar's bodies. Upon further investigation, it was determined that there was no cure on the planet and that Goran'Agar was a genetic anomaly. (DS9: "Hippocratic Oath")
Another project Bashir worked on at this time was a treatment for the Teplan blight, a fearsome bioweapon used by the Dominion to punish at least one planet, Teplan, for resisting them. However, his initial attempt to treat a number of patients ended disastrously with Bashir discovering too late that Dominion had prepared the weapon to fatally accelerate its symptoms when subjected to the electromagnetic fields of modern medical equipment. Although deeply despondent at this failure, Bashir inadvertently discovered an in-vitro vaccine that would allow the population to give birth to children immune to the blight. Despite this breakthrough, which earned a commendation from his superiors, Bashir still researched the disease for some time before apparently giving up and presumably delegating the project to Starfleet Medical. (DS9: "The Quickening")
In late 2374, Bashir was selected by Luther Sloan, a member of the covert Federation intelligence group, Section 31, as a potential operative. While the crew of DS9 believed he was attending a medical conference on Casperia Prime, he was abducted by the group and placed in a holographic simulation to determine his potential of being a Section 31 operative. Although offered a position as part of their organization, he turned down the offer. (DS9: "Inquisition")
A year later, Bashir was contacted by Sloan to serve as an operative for Section 31 during Bashir's trip to lecture at a conference on Romulus. Sloan led Bashir to believe that he was planning to assassinate the chairman of the Tal Shiar, Koval. In reality, it was an operation to prevent Kimara Cretak from ascending to a position on the Continuing Committee. (DS9: "Inter Arma Enim Silent Leges")
Several months later, Bashir and O'Brien realized that Section 31 was responsible for the morphogenic virus that was killing the Founders of the Dominion, as well as their friend Odo. Bashir sent a false message to Starfleet Medical, informing them that he had found a "cure". Sloan traveled to Deep Space 9 with the intent of destroying the cure. Bashir and O'Brien were successful in restraining him and, using Romulan mind probes, were successful in extracting the cure from Sloan's mind before he died. (DS9: "Extreme Measures")
Due to his genetic enhancements Julian, in many ways, possessed a superior physiology to other Humans. His intellect was the most obvious example of this, as he was able to perform complex computations faster than a computer (DS9: "A Time to Stand", "Rocks and Shoals"), and his total recall was almost absolute. (DS9: , "Inter Arma Enim Silent Leges") This also made him one of a few Humans who could play Tongo on a Ferengi level, and got to the point that he could beat several experienced Ferengi after a few games. (DS9: "Extreme Measures", "Change of Heart")
Physically he was also enhanced, although his physical abilities were mostly less remarkable. His hand-eye coordination was greatly enhanced to the point where he could hit the smallest part of a dart board with ease at over eight feet, (DS9: "Doctor Bashir, I Presume", "Extreme Measures") his hearing was also enhanced beyond that of a normal Human (DS9: "Statistical Probabilities"), and his reflexes were closer to a Vulcan. (DS9: "Take Me Out to the Holosuite")
Bashir's great-grandmother's name was Watley, and she served as a Starfleet officer during the mid-23rd century. In 2373, when the USS Defiant traveled back to 2268 by way of the Orb of Time, he encountered a Lieutenant Watley aboard the USS Enterprise. Bashir became momentarily convinced that Lieutenant Watley was his great-grandmother, and that he may be facing a predestination paradox. Since no one ever knew his great-grandfather, he thought that he might be destined to fall in love with Lieutenant Watley and become his own great-grandfather. (DS9: "Trials and Tribble-ations")
Bashir's best friend was Miles O'Brien. At first they did not get along; O'Brien felt that Bashir was annoying. This all changed when both men were marked for assassination after helping to destroy biological weapons. O'Brien was wounded, and Bashir helped save him. They enjoyed playing darts and racquetball. Together they had many adventures in the holosuites, the most noteworthy being the Battle of Britain and The Alamo. They even built a scale model of the Battle of the Alamo. (DS9: "The Storyteller", "Armageddon Game", "Rivals", "Homefront", "The Changing Face of Evil")
When O'Brien was given twenty years of prison memories for a crime he did not commit by the Argrathi and could not adjust, he attempted to kill himself. One of the false memories was that he had killed his best friend in prison. It was Bashir who was able to talk him out of the attempt and get him help. Bashir was dismayed when during the final battle of the Dominion War, O'Brien told him he was leaving for Earth to become a professor at Starfleet Academy. (DS9: "Hard Time", "What You Leave Behind")
Although Bashir fell in love with Ezri Dax in 2375, he confessed that he liked Miles "a little bit more", indicating the strong bond of friendship that formed between the two over their seven years of service together on Deep Space 9. (DS9: "Extreme Measures")
Martok and Bashir were both prisoners at Internment Camp 371. Ever since their escape, Martok had always trusted and respected Bashir's medical expertise.
Bashir struck up an unlikely friendship with Elim Garak. He was interested in him because he thought Garak might be a spy. Garak first introduced himself to Bashir during the Tahna Los incident on the station, in such a flirtatious way it confused Bashir and left him quite flustered. They worked together to expose a plot by Dukat to embarrass a Cardassian official who wished to reconcile Cardassia with Bajor.
They had many lunches together. It was during one of these luncheons that Bashir discovered an implant that was killing Garak and he was able to save him. Bahir and Garak often discussed literature during their lunches and frequently debated the differences between Human and Cardassian written works. Garak also became Bashir's sidekick in Bashir's holoprogram about international spies. Together, they saw many combat duties during the Dominion War. (DS9: "Past Prologue", "Cardassians", "The Wire", "Distant Voices", "Our Man Bashir")
Bashir was infatuated with Dax from the very beginning, when they met on a transport to Deep Space 9, and since then desperately pursued her. Quark once said of Bashir as being there every other day "crying into his synthale over her". (DS9: "Emissary", "Playing God") She enjoyed his flirtatious attempts to become intimately involved with her, and according to Ezri Dax, would have entered a romantic relationship with him had Worf not come along. (DS9: "Emissary", "A Man Alone", "Starship Down", "Afterimage")
Melora was an Elaysian who was briefly commissioned to Deep Space 9. She and Bashir had a brief romantic affair, during which Bashir worked on a way to adapt Nathaniel Tero's neuromuscular adaptation theory into a working, long-term solution to Melora's gravity problems. Melora ends up pulling the plug on the treatment, as she wants to be able to return home. She leaves the station and her and Bashir's relationship presumably ends. (DS9: "Melora")
Leeta first showed interest in Bashir in 2371. She faked a cold in order to meet him. They broke up a year later, in 2373. They went to Risa to complete the Bajoran Rite of Separation. Later that year, Nog helped Bashir retrieve his teddy bear, Kukalaka, from Leeta, who had failed to give it back after their break-up. (DS9: "Explorers", "Let He Who Is Without Sin...", "In the Cards")
Bashir first met Sarina Douglas when he was studying a group of genetically-enhanced Humans. The following year, he helped restore her to a normal life by using a neurocortical probe, helping her relate to other Humans. He fell in love with her, and she appeared to fall in love with him as well. In the end Julian's affection for her almost drove her back in seclusion, so he let her go. (DS9: "Statistical Probabilities", "Chrysalis")
When Ezri arrived on the station, Bashir was drawn to her because she carried Jadzia's memories. At first, they tried to avoid each other. But nothing could stop their attraction to each other, culminating in a passionate kiss in a turbolift on the way up to Ops. An annoyed Worf sends them back down, but they didn't appear to notice. They spent their first romantic night together on the eve of the final battle of the Dominion War. (DS9: "The Dogs of War", "What You Leave Behind")
Alternate realities and timelines
In an alternate timeline created in 2373, the USS Defiant was thrown several hundred years in the past, where it crash-landed on the planet Gaia in the year 2173. After the crash, Bashir married one of the ships' crewmembers, Angie Kirby. After several generations, the colony encountered the Defiant once again, where Bashir learned that the planet was "crawling with Bashirs". He made a special point to get down to the planet to meet some of his descendants. While on the surface, Bashir surveyed of the settlement's clinic to determine what supplies needed to be left behind, where he met his great-great-great-great granddaughter: the doctor. She made quite a fuss over Bashir, whose "healing touch" was something of a legend on the planet. (DS9: "Children of Time")
In a future alternate timeline, during the early-2400s, Bashir held the rank of full commander, and was among the crew aboard the USS Defiant that traveled to the Bajoran system in an attempt to recreate the conditions that caused the disappearance of Captain Sisko. It was revealed during this timeline that he had multiple offspring. Bashir also commented on how long it had been since he used a two-dimensional control panel, and later suggested they drop by Morn's bar for a drink. (DS9: "The Visitor")
Bashir was holographically duplicated at least once.
- In 2373, Doctor Lewis Zimmerman based his initial test version of the Long-term Medical Holographic program on Bashir's likeness. (DS9: "Doctor Bashir, I Presume")
- DS9: ; all episodes except for:
- "Blood Oath"
- "The Collaborator"
- "Through the Looking Glass" (only as mirror Julian Bashir)
- "Shattered Mirror" (only as mirror Julian Bashir)
- "Rapture" (only as Changeling replacement)
- "The Darkness and the Light" (only as Changeling replacement)
- "The Begotten" (only as Changeling replacement)
- "For the Uniform"
Julian Bashir was played by Alexander Siddig.
In March 2015, Executive Producer Rick Berman related on his twitter account, "When I first saw Siddig on film I wanted him as Sisko. Then I learned he was in his 20s (couldn't have a teenage son) so he became the doc."  Another actor who auditioned for the role was Edward Rawle Hicks. 
Julian Bashir was originally called "Julian Amoros", and his name was only changed at the last minute prior to the filming of "Emissary". In the "DS9 Bible", while most of the characters had several pages describing their back-story and giving information on their psychology, Amoros' description was simply, "a Human male in his mid-twenties; may have an accent depending on casting." In the first draft script of "Emissary", Amoros was described as "Human, male, mid-twenties, wide shouldered with a boyish face, trying to appear confident." The character was described in much the same way in the final draft of the "Emissary" script, though his surname was changed to "Bashir" by then and the latter statement of the initial description was now altered to refer to him as "cocky with a little too much confidence." As Alexander Siddig pointed out in 2002, "He was a completely blank canvas, no one knew anything about him." He believes that the only reason the character was created was because the producers knew there had to be a doctor on the show, but beyond the fact that he was a doctor, "they were all scratching their heads." (Crew Dossier: Julian Bashir, DS9 Season 6 DVD special features)
In "Emissary", it was stated that Bashir was twenty-seven, which would make his birth date late in the year of 2341 or early in 2342. This is confirmed by the mention of his birth date in 2341 in "Distant Voices".
According to Michael Piller, "We wanted to do something that very rarely happens on Star Trek; we wanted to create an imperfect character, we wanted to create the tenderfoot in the old western town, somebody who's ready to go out to the great unknown, but isn't quite ready for it. We saw the potential of having the character grow into his role as a hero." (New Frontiers: The Story of Deep Space Nine, DS9 Season 2 DVD special features) Ira Behr elaborates on this, "Doctor Bashir began as probably the least liked character on the series by the fans, tremendous resistance to Dr. Bashir for some reason. They felt he was too green, too arrogant, too wet-behind-the-ears, too fumbling. And we said 'We are going to make this character great, because Sid is a great actor, and we are going to make this character great.' And again, over the years, this character has grown by leaps and bounds." (Crew Dossier: Julian Bashir, DS9 Season 6 DVD special Features)
Speaking in 1992, shortly after filming had begun on "Emissary", Siddig El Fadil said of Bashir, "He's a brilliant medic, knows very much how to apply himself, and cares very much about being a doctor, and people, and general things in that sense. But there's a chink there, something that makes him lose his concentration a little bit, and it's his zealousness, his enthusiasm for things. But he also has a romantic vision of what he's capable of, which might get him into an awful lot of trouble." (Hidden File 08, DS9 Season 1 DVD special features)
Making Bashir genetically engineered in "Doctor Bashir, I Presume" was a last-minute decision. As Ira Steven Behr explains, "at the time we were working on "In Purgatory's Shadow" and "By Inferno's Light", we had no idea that Bashir would turn out to be genetically engineered… even though it was the very next episode…" In Jimmy Diggs' original version of "Doctor Bashir, I Presume", the Bashir/Zimmerman plot was the B-story. The producers were uninterested in the A-story, but they loved the idea of Zimmerman using Bashir as the model for the LMH and decided that it was worthy of being an A-story in and of itself. However, they were aware that a comedy show dealing with holographic doctors would not be enough to sustain an entire episode, and they decided that to make things more interesting, Zimmerman would have to discover some dark secret from Bashir's past. As René Echevarria says of Ronald D. Moore, "his instinct was that there needed to be some big secret that Zimmerman uncovers, but we couldn't, for the life of us, think what it would be." According to Moore, "I kept saying 'What's the secret of Bashir's past? What's the thing that this guy Zimmerman is going to find that's so interesting?' I remember that René and I started talking about genetics, and René pointed out that genetic engineering is one of the things that is oddly missing in the Star Trek universe. It's a concept that's very much out there in science fiction, and even in the real world of science, but in Star Trek, it's virtually never discussed, aside from the fact that there was this thing called the Eugenics Wars at some point, and Khan came out of it." That conversation ultimately led Moore to come up with the idea that Bashir was genetically enhanced. (Star Trek: Deep Space Nine Companion) Alexander Siddig was not happy about this sudden development in his character: "I didn't know about it on Tuesday, and on Thursday the script arrived – we started shooting on Friday. I was so shocked. You know you get the impression that maybe the producers sit down and talk about strategies and character arcs with actors but this thing came out of the blue and pissed me off so royally." Siddig interpreted the change as an attempt to turn his character into Data, a tendency which he fought against by deliberately playing any "Data-esque" lines badly. 
The relationship built up between O'Brien and Bashir was very important to all of the writers, as well as both actors. According to Ronald D. Moore, after the scene where they sing "Jerusalem" together in "Explorers", all of the staff writers wanted to write scenes involving their friendship. According to Alexander Siddig, "it's been said, by even the producers, that O'Brien and Bashir are the only real friendship that's ever happened on Star Trek. These two really are friends. It's not like some kind of odd couple scenario, like Spock and Kirk. It's a real friendship. These people talk about inane things, and I think that's been really refreshing." Robert Hewitt Wolfe elaborates, "It was just great. There was just great chemistry between the two actors, great chemistry between the two characters. It was brilliant of Michael and Rick to create these two characters as foils for each other. And to then see this relationship develop over the years till they're best friends, till Miles actually likes Bashir kind of almost better than his wife some days, which is very real, I mean there's days that everybody, you know, it's easier to be friends with a friend than with your wife some days." (Crew Dossier: Miles O'Brien, DS9 Season 5 DVD, Special Features) Ira Behr goes even further, and cites it as his favorite relationship in all of Star Trek; "The relationship between Bashir and O'Brien is the best relationship, the best friendship, in the history of the franchise. Spock and Kirk were still about the captain and his number one. This is a friendship with two equals, two guys. It's a wonderful thing to watch how this relationship has grown." (Crew Dossier: Julian Bashir, DS9 Season 6 DVD special features)
Early in the run of Star Trek: Deep Space Nine, Michael McGreevey pitched a story to the writers that featured Jadzia and Bashir falling in love. McGreevey commented "It was a love story, a simple concept. I don't know why they didn't want to do it. The symbiont inside Dax becomes ill, making her ill, and Dr. Bashir must separate them in order to treat the symbiont. We would come to see the personality of Jadzia, which of course is different from Dax. Bashir falls in love with her, and she feels for him, too. But the most important thing in life is to be joined with the symbiont. Bashir realizes that the only way to save the symbiont is to put it back into Jadzia, and thereby lose the girl he loves". (The Official Star Trek: Deep Space Nine Magazine issue 8)
According to the video game Star Trek: Starship Creator, Bashir was born in London. The cover art for the Section 31 Novel Control states his date of birth to be August 29, 2341 (though this date of birth is never confirmed officially).
In the DS9 relaunch novels, Bashir and Ezri break up when Ezri began to pursue a more command-based career path after incorporating her past hosts into her personality. Ezri went on to receive a battlefield promotion to Captain of the USS Aventine when most of the ship's senior staff were killed, and remained as its commanding officer.
In Zero Sum Game, Bashir reunited with Sarina Douglas and renewed their relationship during a mission to sabotage a Breen shipyard. Bashir contemplated a transfer to Starfleet Intelligence as he now felt more like just another Starfleet doctor without the opportunities for "frontier medicine" he had originally come to the station to practice, as well as the fact that almost all of his old friends in the station's command structure had left the station. However, Bashir eventually decided to remain on Deep Space 9 in Plagues of Night.
As a result of his work to save the Andorians from extinction (by providing them with extremely classified information concerning a meta-genome) in A Ceremony of Losses, Bashir was court-martialed by Starfleet and dishonorably discharged. However, due to a pardon from the newly-elected Andorian Federation President, the discharge was changed to an honorable one in Disavowed.
Bashir and Douglas continued their quest to destroy Section 31. Ultimately, in Control, he discovered that Section 31 was being run by an artificial intelligence called Uraei, also known as "Control", which had its origins in the 22nd century. With Data's help, he managed to eliminate Uraei, but in the process, Douglas died and Bashir himself was rendered catatonic. Section 31 was exposed to the public and dismantled but unknown to anyone, the Control persona survived independently of Uraei and went into hiding. Bashir, still catatonic, was taken to Cardassia where, as of Enigma Tales, he remains under the care of Castellan Garak's staff.
Bashir appears in the "Victory is Life" expansion of Star Trek Online, played once more by Alexander Siddig. Set over 30 years after the events of DS9, Bashir had retired from Starfleet to run a private practice on Trill, but was asked to return to Starfleet by now-Kai Kira and Captain Ezri Dax due to the Hur'q threat. Despite the promotional materials showing him with the rank of Captain, he appears in game at the lower rank of Lieutenant Commander. During the campaign in the Gamma Quadrant, Bashir accompanies Kira and the player character to the moon where Kai Opaka had been marooned four decades before ("Battle Lines") and administers a cure for the microbes that keep Opaka and the now-peaceful Ennis and Nol-Ennis prisoners trapped on the surface, allowing them to leave. When Quark and his Ferengi team recover the Sword of Kahless from an Iconian dreadnought, Bashir is able to determine that its blade was created from a four-thousand year old Hur'q carapace, originally from the planet Havas-Kul in the Gamma Quadrant. In the mission "Home", Bashir and the Vorta Loriss work to introduce a ketracel-based compound into the Hur'q's organic computer system in order to restore their cognitive function, an effort that is successful due to the sacrifice of the Jem'Hadar Elder Dukan'Rex. At the mission's end on DS9, he mentions that he will be deployed to Havas-Kul aboard the USS Aventine, and that he is also married to the ship's captain (confirmed, like in the DS9 relaunch novels, to be Ezri Dax in the STO fiction blog "Spores", which links to the "Age of Discovery" expansion; "Home" also establishes that they have multiple children). Bashir also replaces the Andorian doctor Ghee P'Trell in the earlier mission "The Ultimate Klingon", dealing with a mad scientist working to create Klingon Augments.
The alternate reality version of Julian Bashir appears in the third issue of the Star Trek: Ongoing story arc The Q Gambit where he serves as a doctor at a Dominion labor camp on Bajor. When the sciences division of the USS Enterprise are taken prisoner and brought to the camp, he meets Spock and Dr. Leonard McCoy after saving McCoy from be brutalized by a Cardassian overseer. They explain to Bashir that they were brought over a hundred years into the future by Q and he explains to them that the Federation no longer exists. He then eagerly offers to help them by paying Quark off to smuggle Spock and McCoy off-world in cargo containers pass the Vorta supervisors in exchange for Romulan ale.