The 34-year-old Bulger could have continued playing this season and had opportunities to do so. There was interest in him from several teams, including Arizona, before the Cardinals traded for Kevin Kolb. But after mulling over his options, Bulger felt the best scenario was to retire.
Bulger singled out former Rams coach and current Chicago Bears offensive coordinator Mike Martz, who made him a starter, in thanking those who supported him through his career.
"I am grateful to all my former teammates, coaches and my family," Bulger told ESPN.com on Wednesday morning. "I have a special place in my heart for coach Martz for giving me an opportunity.
"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."
During his NFL career, Bulger threw for 22,814 yards, 122 touchdowns, and 93 interceptions.
Adam Schefter is ESPN's NFL Insider.