Haas, seeded third this week, won nearly three-quarters of the points on serve and dropped his serve once on the day in ending Kohlschreiber's hopes of repeating as BMW Open champion.
The fourth-seeded Kohlschreiber lost his serve once in each set but only managed two break chances in the match. He had a slight advantage (63 percent-58-percent) in landing his first serves but Haas won 34-of-40 points when he got in first serve in.
Haas, born in Hamburg, Germany, snapped a three-match losing streak in finals. His most recently win was June 2012 in Halle, Germany, and before that was the 2009 tournament in Halle. He also won in Stuttgart, Germany, in 2001 and had runner-up finishes in Stuttgart and Munich in 1999 and Munich again in 2000. He is 14-12 overall in finals appearances.
Kohlschreiber, who won the ATP's Munich stop in 2007 and 2012, was looking for a fourth title in Germany but fell to 4-5 in title matches. He was also born in Germany.