He played college football for the Florida State Seminoles and was selected in the first round by the San Diego Chargers in the 2006 NFL draft.

Cromartie holds the record for the longest scoring play in NFL history after returning a missed field goal 109 yards for a touchdown in 2007.

He was a member of the FSU track team that won the ACC Championship in 2004, where he placed 10th in the 200 meters with a time of 21.35 seconds.

[9] He ran a career-best time of 46.39 seconds in the 400 meters at the NCAA Division I Championships, placing 6th in the prelims.

[13][14] Despite being removed from competitive football for an entire year, Cromartie was still selected as the 19th overall pick of the first round of the 2006 NFL draft by the Chargers.

The Chargers put Cromartie in the endzone to return the field goal in case of a missed kick.

Cromartie intercepted the football, came down with both feet in bounds, two inches from the back of the end zone, and began the return.

Cromartie returned the missed field goal 109 yards for a touchdown at The Metrodome, setting a record for the longest play in NFL history.

The next week Cromartie made his first NFL start in place of the injured Quentin Jammer and intercepted three passes thrown by Peyton Manning of the Indianapolis Colts; the last of which was a leaping one-handed interception in front of Colts WR Reggie Wayne.

[17] On November 24, Cromartie became the starting cornerback, replacing Drayton Florence (who became a free agent at the end of the season).

In the AFC Divisional game against the Colts, Cromartie recorded another interception against Peyton Manning, and his defensive efforts during the game (including a forced fumble against Marvin Harrison) helped the Chargers knock off the defending champion Colts.

[19] In his first regular season game with the Jets, Cromartie intercepted an errant throw from Joe Flacco which he returned 66 yards.

[21] His kickoff return in the wild card round against the Indianapolis Colts helped to set up Nick Folk's game-winning field goal.

[21] In the home opener against the Dallas Cowboys on September 11, Cromartie gave up two touchdowns to Dez Bryant and Miles Austin but rebounded the following week intercepting two passes by Luke McCown.

He left the game in the second half and was transported to Eden Medical Center where he was diagnosed with bruised ribs and a pulmonary contusion.

[25] During the 2012 season, after Darrelle Revis went down due to a torn ACL, Cromartie became the #1 cornerback and performed well, finishing the year with 3 interceptions, 13 passes defended, and 30 tackles in all 16 games started.

[35] In October 2023, Antonio Cromartie was hired as a defensive analyst for the Saint Augustine University's football team.