T. J. Lang attended Eastern Michigan University. As a freshman, Lang played in all 11 games as a defensive lineman, recording 11 tackles, in the 2005 season. As a sophomore in 2006 Lang moved to offensive tackle and started all 36 games over the next three years.

Lang was selected in the fourth round (109th overall) by the Green Bay Packers in the 2009 NFL Draft. On July 7, 2009, he signed a contract with the Packers. Lang started his first game at the left tackle position versus the Cleveland Browns due to an injury to Chad Clifton.

On August 14, 2012, Lang signed a four-year contract extension with the Packers worth $20.8 million and a $5.5 million signing bonus through the 2016 season.

For his play during the 2016 season, Lang earned his first Pro Bowl appearance in the 2017 Pro Bowl.

On March 12, 2017, Lang signed a three-year contract with the Detroit Lions. He started 13 games at right guard in his first season in Detroit, on his way to his second Pro Bowl.

In 2018, Lang started six games at right guard, missing three games due to head, back, and neck injuries, before being placed on injured reserve on November 14, 2018.

On March 29, 2019, Lang announced his retirement from the NFL.