Alert status one, also known as defense condition one, was a Klingon alert signal announced during the preparation for battle.

In 2373, first officer Worf issued an alert status one on board the IKS Rotarran after detecting a Jem'Hadar patrol ship running active polaron scans of a sector outside of the Cardassian border. (DS9: "Soldiers of the Empire")

In 2374, while performing convoy escort duty, the Rotorran was again put on alert status one after a Jem'Hadar fighter was detected. After several minutes, it turned out that it was just a battle simulation that Alexander Rozhenko had forgotten to switch off. General Martok then stood the ship down from the alert. A short time later, the ship was put on alert when a group of three Jem'Hadar fighters attacked the convoy. The Rotarran was damaged but successfully managed to destroy them. (DS9: "Sons and Daughters")

In 2375, General Martok called for the IKS Ch'Tang to set defense condition one prior to the ship's arrival and attack on the Dominion base on Trelka V. (DS9: "Once More Unto the Breach")

Along with the alert, the crew were ordered to prepare for combat operations, indicating that alert status one may be the equivalent of a red alert aboard Starfleet vessels.