Thornton and the Bruins have agreed to a two-year extension worth an average of $1.1 million per season, according to TSN's Bob McKenzie.
The 34-year-old Ontario native has become an integral member of the Bruins team over the past few seasons, most famously returning from the bench to help the B's struggling fourth line during last year's Stanley Cup run.
Thornton isn't much of a goal scorer but he has been pretty productive for Boston this season, scoring four goals and eight assists in 70 games. The hard-hitting forward has averaged 9:06 of ice time per game and of course the 19 fights.
The winger is in his fifth season with B's, after coming over from Anaheim as a free agent in 2007. Thornton would have been an unrestricted free agent in the offseason, along with teammates Chris Kelly, Gregory Campbell, Daniel Paille and Joe Corvo.