Stanley took a three-shot lead to the 72nd hole but gave all three away with a third shot that spun back off the green and into the water hazard short of the flagstick, followed by a three-putt.
After the two players made birdies on the first playoff hole (No. 18), Snedeker, who shot 5-under-par 67 in regulation, made par on the par-3 16th. Stanley, who was looking for his first PGA Tour win, missed his par putt.
The win was the third in Snedeker's career.