It just gave the Oklahoma City star a chance for a career high and the first 50-point game in the NBA this season.
Durant scored 52 points, including the go-ahead basket with 16.9 seconds remaining in overtime, and the Thunder turned away a big Dallas rally for a 117-114 victory that extended their winning streak to six games and ended the Mavericks' season-best run of four straight.
A night after being voted a starter for the All-Star Game, Durant had a little trouble from the field, going 13 of 31. But he was 21 of 21 from the foul line, and the Thunder made all 12 of their free throws in the fourth quarter.
That looked as though it would be enough to hold off the Mavericks until Mayo hit his tying 3-pointer with two defenders in his face with 2.3 seconds left in regulation.
Vince Carter, who kept the Mavericks close when Oklahoma City threatened to blow them out in the first half, had a season-high 29 points. He hit three free throws to start overtime when he was fouled on a 3-pointer, but Durant answered with a pair of freebies on the other end.
Durant went on to score nine of Oklahoma City's 12 points in overtime and had three go-ahead buckets to help the Thunder avoid losing for the first time in 28 games when leading after three quarters. The Thunder blew a 14-point lead in the second half.
"Experience has helped me a lot," said Durant, whose previous career high was 51 against Denver last February. "If I look like I'm out there panicking, my teammates will look at me and feel the same way. I've got to be cool. If I miss a shot, so be it. I'm sure opportunity will come back around sooner or later."
The fact that Durant wound up going to the line 21 times didn't sit well with Mavericks forward Shawn Marion.
"It's hard to beat anybody when you're playing five on eight," Marion said. "That's nuts. Some of them were fouls. Some of them were questionable. But it is what it is."
Dirk Nowitzki bounced back from a dreadful shooting night to score 12 in the fourth quarter, but the Mavericks couldn't get him the ball trailing by two in the final seconds of overtime. Mike James, who came in shooting less than 20 percent but had hit a go-ahead 3 earlier in the extra period, ended up with the ball well behind the arc with the shot clock dwindling. His shot barely hit the front of the rim.
Russell Westbrook, who scored 31, missed a free throw to give the Mavericks one more chance to tie, but Carter's desperation 3 at the buzzer was short.
"The play blew up and Mike ended up with it, and it was unfair to him," Dallas coach Rick Carlisle said. "It was a play that didn't work, and it was my responsibility."
Nowitzki finished with 18 points after starting 1 of 11 from the field, salvaging his 10th straight double-figure game after scoring in single digits the first four games following his return from missing 27 games after right knee surgery.
The Mavericks had six players in double figures for the fourth straight game. Mayo had 18 points and seven assists, and Darren Collison scored 15.
Durant put Oklahoma City ahead 99-98 on a pair of free throws after he was fouled on a drive with 1:32 left in regulation. He hit two more after he was fouled following a rebound of a miss by Nowitzki, and Oklahoma City kept the lead until Mayo's tying 3-pointer.
"He's the best offensive player on the planet," Dallas coach Rick Carlisle said. "I don't think there's any question about that. There's some things we obviously could have done to limit him, and that's on me, too."
Added Nowitzki: "For a guy getting 52, I think this is about as well as you can guard him. Obviously, I think we could have kept him off the line on some occasions where we reach in or he gets to the line because he's Kevin Durant. Twenty-one (free throws) is too much, especially if he shoots them like a layup."
Neither team led by more than three in the final 6 minutes of regulation and overtime.
The Mavericks, who earlier this season tied an NBA record with their 10th straight overtime loss, fell to 1-8 in overtime games this season. Two of the losses have been to the Thunder, who improved to 4-0 in overtime.
"It always seems to be a fourth-quarter game or overtime game this year," Oklahoma City coach Scott Brooks said. "Both teams did not want to lose this game."
The Mavericks trailed 87-79 when Carter hit a free throw and Nowitzki had a tip-in to start a 13-2 run that gave Dallas its first lead since the first quarter. Nowitzki's free throws gave the Mavericks the lead at 90-89 with 6:41 left.
Nowitzki was called for a technical foul during a timeout, and Thunder C Kendrick Perkins picked up one when he got in Chris Kaman's face after Perkins was called for a foul for bumping Kaman while they were battling for a rebound. ... Mavericks F Elton Brand recorded the 400th double-double of his career Wednesday against Houston. He had 11 points and 10 rebounds. ... Durant will start in the All-Star game Feb. 17 in Houston. His coach, Brooks, won't be in charge. Brooks is ineligible to lead the Western Conference stars because he did it last year. "It was pretty cool to be able to meet some of the players and see how they are off the court," Brooks said. "Whoever gets it will have a great experience in a great city."
Information from ESPNDallas.com's Tim MacMahon and The Associated Press was used in this report.