Smith was selected 97th overall in the 2006 NFL Draft. Smith had been rising on many draft boards in the weeks leading up to the draft as he was praised for his instincts and physicality on the field. The Jets signed Smith to a contract on July 21, 2006.
Smith recorded 27 tackles in 15 games during his rookie season. He also added two interceptions, recording his first against former Cleveland Browns quarterback Charlie Frye.
In 15 games, Smith recorded 40 tackles and 5 passes defensed.
On September 28, 2008, Smith was fined $50,000 and suspended one game because of a helmet-to-helmet collision with Anquan Boldin of the Arizona Cardinals, which caused Boldin to be hospitalized.
Smith finished the season with 32 tackles, 4 passes defensed and an interception.
Smith was primarily utilized as a back up defender and on special teams. In 16 games, he recorded a career high 48 tackles, 6 pass defensed and an interception.
In the team's week two matchup against the New England Patriots, Smith delivered a hit to wide receiver Wes Welker and was flagged for hitting a defenseless receiver. Smith apologized to Welker during the game, which Welker accepted, and was later fined $7,500 by the league.
Smith re-signed with Jets on July 30, 2011 to a three-year deal worth $7.5 million.
Smith suffered a medial collateral ligament (MCL) injury on his left knee during the August 10 preseason loss to the Cincinnati Bengals. An MRI came back negative. Smith was eventually knocked out for the entire 2012 season. He was released from the Jets on February 19, 2013.
Smith was hired by the New York Jets on February 10, 2014 as a seasonal intern coach.
Smith was hired by the Buffalo Bills to be the assistant special teams coach on January 15, 2015. He served two seasons in Buffalo on Rex Ryan's staff before being dismissed by new coach Sean McDermott.