The Swiss now goes into the final Grand Slam of the season in eight days as a legitimate threat after reaching the final last week in Toronto and claiming his 16th win without a loss against Spain's Ferrer over an 11-year span.
The world number three is unbeaten in six finals in Cincinnati, also winning the tournament in 2005, 2007, 2009, 2010 and 2012.
Federer added a third title of 2014 to those he won in Dubai and Halle. He ran his career title total to 80 from 121 finals.
He increased his match-win lead this season on the ATP to 49 victories, with Rafael Nadal -- his US Open bid in doubt because of injury -- trailing second on 44.
Federer, 33, won his 22nd Masters 1000 trophy, second to Nadal's 27 in the elite category.
Federer, who has played Cincinnati for a decade and a half, was glad to finally win his biggest title since Cincinnati in 2012, when he also won Wimbledon.
The father of two sets of twins joked that it was about time he brought his brood a substantial trophy to play with.
"I finally got a big trophy for kids," he said Sunday. "I've been bringing home some smaller ones. I keep telling them they are still trophies, but this one should satisfy them."
After a finals loss a week ago in Toronto to Jo-Wilfried Tsonga, Federer said Sunday that he had considered not playing this event and saving himself for the US Open.
"I had to try to back up a tough week from last week, I didn't think it was possible," he said.
"For just a day or so on Monday, I was considering not playing. We don't need to take chances here.
- 'I played with less pressure' -
"I need to be smart about how much I play, when I play, and how do I feel.
"In practise I felt like I was recovering quickly, and I gave it to a go. I played with less pressure. You never know how you will end up feeling midway through the week."
Federer said his decision to carry on proved to be the right one.
"It got better and better as the week progressed. I served clutch when I had to," said the 17-time Grand Slam champion. "So I'm very happy about the week, overall it went from good to great."
Federer ran away with the opening set but suffered a lapse in the second as Ferrer took it to 5-0 and needed three set points to finally level at one set each.
But after a rare mid-match visit to the locker room after losing the second, Federer stormed back to take the match by the throat, breaking for 3-1 in the third and putting his Spanish opponent under pressure as Ferrer saved four set points to hold for 2-4.
It was only a matter of time as Federer's shot making began to tell. The second seed won a love game for a 5-2 margin before breaking Ferrer for the final time to win.
"I made the final," said the good-natured Ferrer, winner of one Masters title. "But I can never beat Roger, he's too much for me.
"I'm still lucky to be playing with the best in the world. Roger deserved to win the title."
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