Bulger was selected for the Pro Bowl twice and passed for 22,814 yards, 122 touchdowns and 93 interceptions.
"I am grateful to all my former teammates, coaches and my family," Bulger told ESPN.com. "I have a special place in my heart for coach Martz for giving me an opportunity."
It's not that Bulger didn't have offers to continue playing in 2011. A league source told The Baltimore Sun that a handful of teams were interested in the quarterback this offseason.
Bulger was drafted out of West Virginia by New Orleans in 2000, but never played a game for the Saints. He latched on with St. Louis in 2001 and eventually succeeded Kurt Warner as the starter.
He passed for more than 3,800 yards in a season three times, including a career-best 4,301 yards in 2006, the only season in which he played all 16 games.
"Moving forward, I'm excited to continue doing work through my foundation to help the men and women in uniform who risk their lives every day so we can enjoy the game of football," he told ESPN.com.
The Associated Press contributed to this report.