Karlovic, playing in the final match Tuesday, defeated Daniel Brands 6-7 (4-7), 7-5, 7-6 (7-3). He dropped just eight points over 18 games serving, posting an 87 percent win rate on serve.
Brands took three-quarters of the points on serve himself but suffered the only break of the match to lose the second set and fell behind 0-4 in the third-set tiebreaker, allowing Karlovic to put the match away with his serve.
Karolivc had 16 aces in the first set, 13 in the second and 15 in the third while tying the tour record set by Mark Philippoussis in 1995.
German qualifiers Michael Berrer and Bjorn Phau both took out local wild-card entrants to claim first-round wins. Berrer defeated Borna Coric 6-4, 3-6, 6-4 and Phau was a 6-3, 6-4 winner over Ante Pavic.
Berrer's win took nearly 2 1/2 hours and came down to the third set, during which he saved three break points and won almost 70 percent of the points on serve.
Phau had three breaks in the first set and another in the second. He lost only six points in five games serving in the second set.
Also Tuesday, Lukas Lacko beat Jan-Lennard Struff 6-4, 6-4 with 10 aces and Dusan Lajovic ran past Pedja Krstin 6-2, 6-3 in 58 minutes.