"I am very humbled by the request to stay on, and I look forward to building on the great momentum our game has seen in recent years," Selig said.
He was named acting commissioner Sept. 9, 1992, after Fay Vincent stepped down, but was not given the job on a permanent basis for another six years.
Selig's contract was to have run out Dec. 31, 2012. He will be 80 years old when his new deal expires.
During Selig's tenure the sport has expanded its playoff system and seen the creation of interleague play. Selig was also responsible for awarding home-field advantage in the World Series based on the winner of the All-Star Game.