Nick Collison made it three Thunder players with double-doubles with 13 points and 10 rebounds.
Durant erased a five-point deficit with a minute left in regulation, hitting a runner and a 3-pointer that sent the game into overtime. The Sixers scored only two baskets in the extra 5 minutes.
Jrue Holiday and Lou Williams each scored 22 points for the Sixers. Elton Brand had 13 points and 15 rebounds.
Durant, the NBA's leading scorer, was 13 of 26 from the field and all 16 boards were defensive ones.
The Sixers played one of their most exciting games of the season in front of a surprisingly strong crowd of 19,283. Their playoff push - coupled with Durant's appearance - made this one a rare must-see game in Philly.
Both teams delivered in a fourth quarter where each clutch basket was matched by a clutch basket.
The Sixers created some separation late in the period. Williams, who scored nine straight points in the quarter, started his run when he faked a pass to Thaddeus Young and took himself to the basket for the three-point play.
Williams was positioned with his back to Oklahoma City's bench when Brand fed him the ball and he buried a 3 for a 101-96 lead.
The Thunder, of course, are never out of a game with Durant on the floor. He fired a 3 over Andre Iguodala's outstretched arms with 6.2 seconds left that tied the score at 101-all.
Iguodala was whistled for an offensive foul on a drive down the paint with 1.9 left to give the Thunder one last chance to win. Durant missed his long-range shot at the buzzer and the Thunder were set for their eighth overtime game of the season.
Durant hit three 3s, none more dazzling than one with 17 seconds left in the third. He caught the ball behind the arc, swung his arms in a circular motion and tossed up the ball - good! And he was fouled by Young.
Durant smiled as he nodded in approval at the Thunder bench. He sank the free throw for the four-point play and an 82-80 lead.
Durant's quick release on a 3 in OT startled the Sixers and put the Thunder up 108-105. Westbrook followed with a long jumper and that was the game.
Durant had 13 points and 10 rebounds in the first half as the Thunder shot 56 percent from the field. Jodie Meeks and Holiday scored 11 apiece and the Sixers shot 58 percent from 3-point range for a 55-all score at halftime.
Notes: The Sixers had a three-game winning streak snapped. ... 76ers director of statistical information Harvey Pollack turned 89. He is the NBA's only original active employee.