BOSTON -- Paul Pierce scored 34 points, including a 3-pointer at the start of the second overtime to give Boston the lead for good, and the Celtics held on to beat the Dallas Mavericks 117-115 on Wednesday night.
Rajon Rondo had 16 points, 15 assists and nine rebounds, and Kevin Garnett added 16 points for Boston.
O.J. Mayo scored 24 points for Dallas, and Shawn Marion had 16 points, 11 rebounds and seven assists.
Pierce made five of six free throws in the second overtime to help the Celtics clinch their second straight victory. With his basket with 59 seconds left in the first overtime, he surpassed 23,000 points in his career -- the 25th player in NBA history to reach the mark.
Boston led by 14 in the third quarter and eight after the first basket in the fourth before Dallas chipped away at the deficit and tied it at 92 on Darren Collison's drive to the basket. After Rondo made a jumper, Derek Fisher hit a 3-pointer with 1:47 left in the fourth to give the Mavericks their first lead of the game.
Rondo had a chance to win it at the end of regulation, but Fisher blocked the shot and it floated just a few feet. Pierce also had a chance at the end of the first overtime, but his shot was blocked by Dahntay Jones.
But Pierce came out in the second overtime and hit a 3 to make it 108-105. Mayo's basket made it a one-point game and the tired teams struggled to score until Rondo drove to the basket to give Boston a 110-107 lead with 36 seconds to play.
From there, Dallas was forced to foul.
Pierce sank one of two free throws and Vince Carter hit a 3-pointer with 10 seconds left to make it 111-110. Pierce hit another pair of foul shots and Collison hit two free throws before Pierce and Courtney Lee each made two.
Mayo made a meaningless 3-pointer at the buzzer to make it a two-point final margin.
Jason Terry, who played eight years for Dallas, scored 10 points.
The Celtics never trailed, opening a six-point lead in the first quarter and leading by as many as 10 in the second before Dallas scored 8 of the last 11 points in the half to head into the break down just 48-43.
Boston opened a 14-point lead early in the third quarter before the Mavericks scored 10 of the next 12 points. After Rondo drove to the basket to give Boston a 78-70 lead with the first score of the fourth quarter, the Mavericks went on a 7-2 run -- five points coming from Mayo -- to make it a three-point game.
Dallas cut it to one point with 6:54 left and tied it 92-all on Collison's drive.