The son of the late Commodore Matt Decker, Will Decker was hand-picked by Admiral James T. Kirk to command the U.S.S. Enterprise upon its refitting ca. 2270. But Kirk was on board when the Enterprise was being readied to intercept the V'Ger entity on its way to Earth, and Decker was downgraded to executive officer so Kirk could take the captain's chair. When V'Ger threatened to destroy Earth unless the "Creator" came to it in person, Decker volunteered to go on behalf of the human race. He merged with V'Ger into a glowing, non-corporeal entity, ending his physical lifespan and presumably evolving into a new lifeform. The official record listed Decker as "missing in action."
Prior to his assignment as captain of the Enterprise, Decker was stationed on planet Delta IV, where he was romantically involved with Ilia, a Deltan female who would later be posted as navigator on the Enterprise under Decker's command.