Manassero and Louis Oosthuizen both finished 72 holes in 13-under-par 271 and headed to the 542-yard, par-5 18th hole, which both had birdied in the final hole of regulation, for the playoff.
Both had birdies the first extra hole and pars the second time. On the third playoff hole, Oosthuizen hit his second shot about 24 feet from the hole while Manassero ended up about 12 feet away. Oosthuizen made birdie but Manassero dropped the eagle putt and won the tournament.
It was the third European Tour title for the Manassero, 19, who won at Castellon, Spain, in 2010 and at Malaysia in 2011.
Manassero was the third-round leader after completing the weather-delayed round Sunday before heading out for the final round. He has a 2-under 69 in the final round with a bogey at the 15th-hole before forcing the playoff with a birdie at 18.
Oosthuizen turned in a 4-under 67 but had to overcome three bogeys -- including back-to-back in 12 and 13 -- before an 18th-hole birdie put him in to the lead.
Rory McIlroy fired a 6-under 65 and finished third at 10-under for the tournament and Thomas Bjorn, an early tournament leader, was fourth at 9-under. Bjorn, who shot 68 Sunday, saw his title hopes fade under a 3-over 74 in the third round.