RIO GRANDE, 8 Mar 2015 (AFP) - Cejka, who led after 36 holes, fired a final-round 69 for a seven-under total of 281.
He was joined there by American Tim Petrovic, who posted a 67, Sam Saunders with a 68 and American Jon Curran and Argentine Emiliano Grillo, who both shot 70 on Sunday.
The group went back to the par-5 18th at Trump International for the extra session.
Cejka rolled in a 15-footer for birdie. Saunders was the only player that had a chance to match him, but he missed an eight-foot birdie attempt.
Cejka, whose most recent of four European Tour wins came at Trophee Lancome in 2002, claimed his first US PGA Tour title. He had come agonizingly close to a US win in 2009, when he squandered a five-shot lead in the final round of the Players Championship.
The 5-man playoff might well have been even bigger. Ten players finished within two strokes.
Will MacKenzie, a two-time winner on the US PGA Tour, carded a 4-under 68 to join the group sharing sixth on 282 which also included Boo Weekley (69), Will Wilcox (67) and Scott Pinckney (70).
Third-round co-leaders Chris Smith and Scott Brown, the 2013 winner, both stumbled to 1-over 73s. They ended with a share of 10th on 283 alongside John Daly, Australian Rod Pampling, Spain's Rafael Cabrera Bello and Zimbabwe's Brendon de Jonge.
At 87th in the world, De Jonge was the highest-ranked player in the field of the tournament played opposite the elite World Golf Championships Cadillac Championship at Doral in Florida.
Leading scores after Sunday's final round of the $3 million US PGA Tour Puerto Rico Open (x-won at first playoff hole. USA unless noted, par-72)
281 - x-Alex Cejka (GER) 70-67-75-69, Tim Petrovic 75-71-68-67, Sam Saunders 72-72-69-68, Jon Curran 70-71-70-70, Emiliano Grillo (ARG) 69-70-72-70
282 - Will Wilcox 77-69-69-67, Will MacKenzie 75-69-70-68, Boo Weekley 74-71-68-69, Scott Pinckney 70-71-71-70
283 - Rod Pampling (AUS) 70-71-73-69, John Daly 72-70-72-69, Rafael Cabrera Bello (ESP) 70-75-68-70, Brendon de Jonge (ZIM) 71-70-71-71, Scott Brown 73-70-67-73, Chris Smith 69-73-68-73
284 - Chesson Hadley 71-70-76-67, Brandon Hagy 71-67-78-68, Lee Janzen 72-71-72-69, Jonathan Byrd 70-71-72-71, Chad Collins 70-72-71-71, Martin Flores 72-73-68-71
285 - Eric Axley 71-72-76-66, Jerry Kelly 71-74-73-67, John Merrick 75-70-72-68, Benjamin Alvarado (PUR) 74-70-72-69, Troy Matteson 73-73-69-70