According to ESPN.com, which first reported the news, the deal keeps Mattingly with the Dodgers through the 2016 season.
Mattingly was already under contract for the 2014 season. Exact terms of the extension were unknown, but sources told ESPN that it will keep him in place for the next three seasons.
Mattingly faced an uncertain future last season, and rumors swirled that he was on the verge of getting fired before the team went on a 42-8 run and ultimately won the National League West title by 11 games.
The Dodgers advanced to the NL Championship Series, which kicked in a clause in Mattingly's contract, guaranteeing his $1.4 million contract for 2014.
The Dodgers' 92-70 record last season improved Mattingly's three-year record in Los Angeles to 260-225.
The 52-year-old Mattingly was a six-time All-Star during a 14-year major league playing career, all spent with the New York Yankees. In 1985, Mattingly was the American League's Most Valuable Player.
He served as the Yankees' hitting coach from 2004-06, then as the Yankees' bench coach in 2007.
Joining former Yankees manager Joe Torre in Los Angeles, Mattingly took over as the Dodgers' hitting coach in July 2008, then succeeded Torre as manager in 2011.