The Spaniard was three down at the turn, and was two down to the German with five holes to play. Otaegui won the 14th hole with a par and had three straight birdies on Nos. 15-17 to clinch victory.
Otaegui won six of the eight holes after the turn on the Beckenbauer Course at Bad Griesbach, including the final four, to claim his first win in his 123rd event.
Johan Carlsson of Sweden defeated Spain's Alejandro Canizares, 3 and 2, to win the consolation match.