Brewster quit Criminal Minds in February and will exit the CBS drama at the conclusion of its current seventh season.
Working Class Hero will focus on Jeff (Patton Oswalt), a below-par superhero whose powers fail to impress.
Brewster's new role will see her play Jeff's wife Karen, a medical worker who saves more lives than her 'heroic' husband, reports Deadline.
The series will be co-written and executive-produced by American Dad! co-creator Mike Barker, and produced by 20th Century Fox TV.
Brewster previously played a recurring role on American Dad! and also voices a character in ongoing comedy animation Dan Vs.
Her Criminal Minds co-star Joe Mantegna recently claimed that Brewster could return to the show for guest appearances.
"She's open to coming back, and the character is positioned in a way that she can come back periodically," he explained.