Marin Cilic beat unseeded German Michael Berrer 6-4, 6-7, 6-3 on Sunday to win the Zagreb Indoors tournament for the second successive year and clinch his fifth career title.
The top-seeded Croat took two hours 38 minutes to overcome the 29-year-old German, who put on one of the best performances of his career in his first ATP final.
Berrer had previously upset seeded players Janko Tipsarevic and Viktor Troicki of Serbia and ousted his compatriot Philipp Petzschner 7-6, 7-5 in the semi-finals.
The 1.98 metres tall Cilic won the first set after recording the only break.
However, the world number 65 exerted more pressure and displayed a series of powerful returns in the second. Cilic managed to held serve, and the set came down to a tie-break, which Berrer took 7-5.
In the final set, the 21-year-old Croat broke serve in the fourth game, and saved two break points before firing the 13th ace to seal a hard-fought victory.
Cilic has reached the world's top 10 for the first time this year after winning the Chennai Open last month and reaching his first Grand Slam semifinal at the Australian Open.