In the late 1960s, Guy Gardner appeared as the second choice to replace Abin Sur as Green Lantern of sector 2814. Gardner was a candidate to receive Abin Sur's ring, but Jordan was closer. This placed him as the "backup" Green Lantern for Jordan. But early in his career as a Green Lantern, tragedy struck Gardner as a power battery blew up in his face, putting him in a coma for years. During the Crisis on Infinite Earths, the Guardians split into factions, one of which appointed a newly revived Gardner as their champion. As a result of his years in a coma, Guy was very emotionally unstable, although he still mostly managed to fight valiantly. He has gone through many changes, including wieldingSinestro's yellow Guardian power ring, then gaining and losing Vuldarian powers, and readmission to the Corps during Green Lantern: Rebirth. He later became part of the Green Lantern Honor Guard, and oversees the training of new Green Lanterns. Gardner is designated as Green Lantern 2814.2 within the Corps.

Guy Gardner helped lead the defense of Oa during the events of Blackest Night.

Following his outstanding acts of valour, the Guardians appoint Guy to a unique role and highest rank in the Green Lantern Corps Sentinel, answering directly to the Guardians themselves.