The 23-year-old Italian defeated American Tiafoe 7-6 (7-4) 6-2 despite having been dealing with a hip issue.
In one hour and thirty-seven minutes, top seed Sinner completed his latest triumph after winning the opening set via tie-break.
“It was a really challenging, rough week. I’m thrilled with the game today,” he remarked.
Since Andy Murray of Britain won the Cincinnati Open in 2008 at the age of 21, Sinner is the tournament’s youngest men’s champion.
“It was very tough mentally,” he continued. I really tried to give it my all today, and I had such an incredible run here.
After the semi-finals, we were both quite exhausted.”
At the Australian Open in January, Sinner won his first Grand Slam championship to kick off the year. He subsequently won the last races in Rotterdam, Miami, and Halle after his triumph in Melbourne.
Sinner now focus on the US Open, the year’s last Grand Slam, which begins on Monday at Flushing Meadows, following his victory in Ohio on Monday.
