Zverev has had a breakthrough year in Grand Slam tournaments with his first semifinal at the Australian Open in January and first final at the U.S. Open last month, when he lost to Dominic Thiem.
However, the German hadn't played the final of any regular ATP Tour events until Sunday. Zverev's previous title was at the clay-court Geneva Open in May 2019 and he is now 12-8 in career finals.
Zverev broke Auger-Aliassime's serve in the first game of the match to establish early control. Zverev broke in the second at 3-2 and saved two break points in his next service game to hold off a fightback from the Canadian.
Auger-Aliassime is still waiting for his first career title after losing six finals in two seasons, all of them in straight sets. All three of the finals that the 20-year-old Canadian has played this year have been on indoor hard courts.
The Cologne Indoors is the first of two new back-to-back tournaments the city is hosting after the ATP calendar was modified due to the COVID-19 pandemic.
The second Cologne tournament was already holding qualification matches before Sunday's final in the first tournament took place. It will feature Zverev, former top-ranked player Andy Murray and U.S. Open quarterfinalist Denis Shapovalov.
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