Both sides rested key players for the upcoming playoffs, but the game turned into an entertaining one with Detroit's Kwame Brown hitting a game-tying layup with 8 seconds to play in the fourth quarter.
Bynum then dominated the overtime, backing up a career-high, 26-point performance by Chris Quinn and 22 points from Michael Beasley.
Miami rested Dwyane Wade and Detroit played without Richard Hamilton and Antonio McDyess. Brown led the Pistons with a season-high 17 points.
Detroit, the eighth seed in the Eastern Conference, will play Cleveland in the opening round of the playoffs. Miami, the No. 5 seed, will take on Atlanta in the first round.