In the second season, Sinclair was succeeded as space station Commander by John J. Sheridan (portrayed by Bruce Boxleitner.)

Jeffrey Sinclair is introduced in the 1993 pilot film, Babylon 5: The Gathering, which takes place roughly one year before the first-season episode "Midnight on the Firing Line".

When the Babylon 5 space station was established, Sinclair was appointed as the leader by the Minbari race who were responsible for its creation.

[2][3] Straczynski announced O'Hare's departure via a written statement posted on GEnie on May 20, 1994:This is a mutual, amicable, and friendly separation.

[4] During the filming of Babylon 5, O'Hare struggled with severe mental illness including paranoid delusions and hallucinations.

[5][6] Straczynski emphasized that O'Hare's fans, particularly those of his role as Sinclair, had helped him cope with his struggle in ways "medication never could.

"[7] O'Hare told Straczynski that fans deserved to eventually learn the real reason for his departure, and that his experience could raise awareness and understanding for people with mental illness.

As a result of his departure, there are several minor inconsistencies between the first season and the remainder of the show, most visibly in "And the Sky Full of Stars" and "Babylon Squared."

In literary analysis of characters in pop culture and science fiction, Jeffrey Sinclair has been examined as a hero[8] and leader.