Christiaan Bezuidenhout carded five birdies and five bogeys on Sunday but cruised to a six-shot triumph at the Andalucia Masters.
The South African took a five-stroke lead over Jon Rahm into the final round and looked set to be challenged for a time.
Rahm cut the lead to three when Bezuidenhout bogeyed four out of five holes from the third, yet the momentum soon swung back the way of the leader.
Bezuidenhout carded three consecutive birdies from the ninth, while Rahm faded dramatically as a double bogey at the 12th took him to two over for the day, improving by only one shot across the remaining holes.
He was joined in second place by four other players - Alvaro Quiros, Mike Lorenzo-Vera, Adri Arnaus and Eduardo de la Riva - who also got to four under for the week but could not trouble the leader.
Tournament host Sergio Garcia finished on three under for the tournament.
Victory was Bezuidenhout's first on the European Tour, following up another strong showing at the BMW International Open, where he finished in a tie for third.