Shortly after his birth the family moved to Nigeria, but after his parents separated he returned to the United States with his mother, settling in Chicago and then Santa Cruz, California.

[4] Ayanbadejo was originally signed by the Atlanta Falcons of the National Football League as an undrafted free agent on April 23, 1999.

He served on the practice squad of the Falcons and the Chicago Bears before being picked up by the Winnipeg Blue Bombers of the Canadian Football League in 2000, and spent time with them and the Toronto Argonauts.

In 2004, Ayanbadejo made a play that led to one of the biggest upset comebacks in Monday Night Football history.

[citation needed] While getting sacked, New England Patriots quarterback Tom Brady threw the ball up for grabs.

On October 24, 2011, Ayanbadejo was ejected from a game for striking Jacksonville Jaguars offensive lineman Guy Whimper in the face.

[10] His advocacy rather suddenly became a cause célèbre in September 2012, after Maryland State Delegate Emmett C. Burns Jr. wrote an August 29, 2012, letter to Baltimore Ravens owner Steve Bisciotti, on official Maryland State letterhead, demanding that Bisciotti "take the necessary action ... to inhibit such expressions from your employee."

[14][15] Among others, Minnesota Vikings punter Chris Kluwe wrote a scathing response to Burns, while the Ravens also publicly sided with Ayanbadejo.

[14] In February 2013, Ayanbadejo and Kluwe filed a joint amicus brief with the Supreme Court in support of same-sex marriage, particularly in the case dealing with California Proposition 8.

[18] Later that month Ayanbadejo spoke in support of NBA player Jason Collins, who became the first publicly gay active athlete to play in any of four major North American pro sports leagues.

Obafemi Ayanbadejo was cut by the Chicago Bears on October 1, 2007, after the fullback finished serving his four-game suspension for violating the NFL Policy on Anabolic Steroids and Related Substances.

He has advocated for the passage of the FIT Kids Act, federal legislation that would require school districts to report on students' physical activity and to give youngsters health and nutritional information.