The extension was expected because the Steelers' policy has been to sign a coach before he begins the final season of a contract. The Pittsburgh Post-Gazette reported last week that Tomlin had signed a three-year extension through the 2014 season, and a league source told NFL Network Jason La Canfora that the deal was worth $5 million per year.
Tomlin made $2.5 million per season under the contract he signed upon succeeding Bill Cowher in January 2007. Tomlin is only the Steelers' third coach since 1969, following Chuck Noll (1969-91) and Cowher (1992-2006).
"I have been blessed to have the opportunity to be the head coach for the Pittsburgh Steelers," Tomlin said in a statement released by the team. "I am excited to have the opportunity to live and work in this great city, and to focus on the true matter at hand, which is winning football games and bringing another Super Bowl title to Pittsburgh."
The Steelers were 9-7 and missed the playoffs this past season. They are scheduled to open training camp July 30 at Saint Vincent College in Latrobe, Pa.
The Associated Press contributed to this report.