But the 17-year-old Canadian was quickly stripped of her title after officials ruled she made an illegal turn, resulting in a disqualification.
Overholt, who won a silver medal earlier in the Games, was called for a non-simultaneous touch, meaning she didn't touch the wall with both hands at the same time.
The Canadian team appealed the decision, so all results are still unofficial.
Fellow Canadian Sidney Pickrem, 18, moved up to the silver-medal spot after having the bronze initially.
U.S. swimmer Caitlin Leverenz moved up to gold, while Joanna Maranhao of Brazil ascended from fourth to the bronze spot.