Haase won his second career ATP championship with a 6-7 (2-7), 6-3, 6-2 victory over his German opponent.
Kohlschreiber won the first set in the tie-breaker before rain halted play for more than an hour early in the second set.
Haase was in control after the delay. He lost eight points on his serve in the second set and held Kohlschreiber to 0-for-6 on break points.
Kohlschreiber was 1-of-14 on breaks over the course of the match while Haase converted 5-of-11.