Lt. Gaeta served on board the Battlestar Galactica as the Tactical officer under Commander Adama. When the leaders learned that the Cylons now can look like humans, he was assigned to work with Dr. Baltar on creating a Cylon detector.

Gaeta openly opposed an alliance with the rebel Cylons. After losing a leg during a confrontation with Sam Anders, who was later revealed to be a Cylon, an embittered Gaeta orchestrated a hostile takeover of the Galactica along with Tom Zarek. The failed takeover cost the lives of many crewmen and ended with Gaeta's and Zarek's executions.