The fourth-seeded Spaniard, whose season didn't start until February when he returned from a seven-month injury absence, proved again the eight-time French Open champion is back in peak form after his shock first round exit at Wimbledon.
He beat unseeded American John Isner 7-6 (10/8), 7-6 (7/3) to add the Cincinnati crown to the Montreal Masters title he won a week before, his first ever back-to-back hardcourt trophies.
Nadal is unbeaten on the surface in 2013, having lifted the title at Indian Wells in March as well.
That's an imposing record to take into the final Grand Slam of the season, the US Open, which starts on the hardcourts of Flushing Meadows a week from Monday.
Nadal, however, insisted he wasn't looking that far ahead.
"This title is very important for me, the Open is still a week away. This is the time to enjoy this one. In a few days I'll start thinking about the Open.
"This is amazing, I'm very happy for everything," said Nadal, who took his tally of Masters 1000 titles to 26.
Fourteen of the clay-bred Spaniard's 59 trophies have come on hardcourts, but he had never won on the fast courts of Cincinnati.
He is the first Spaniard to win in Cincinnati since Carlos Moya 11 years ago.
"I have never played well here, this is the first time that I felt like I have," he said.
"John had an amazing week, beating three tough opponents. I'm sorry for today, but if with that serve and that forehand I'm sure he will have lots of chances to win an event like this."
Nadal didn't muster a single break point against the big-serving Isner. But he saved the three he faced and came through in the tiebreakers to seal the victory in one hour and 54 minutes.
Isner produced 11 aces, a minor total by his usual standards.
"I knew I had to come today and play well," said Isner, whose run to the final saw him beat world number one Novak Djokovic and will see him return to the top 20 in the rankings.
"I thought I did but unfortunately I ran into one of the greatest players ever to play the game. Rafa's an incredible champion."
Nadal, who has now won all four career meetings with Isner, won the first set in 92 minutes on his third opportunity -- after denying Isner three set-point chances.
Nadal sprinted away in the second-set decider, taking a 5-1 lead and earning three match points from his opponent's forehand error.
"I never had a chance at a break point, it's so tough to break his serve. I had to be focused in every moment on holding my serve and trying not to give him opportunities,"Nadal said.
Despite the defeat, Isner was upbeat about his game.
"This is the toughest tennis event in the world. The draw is smaller than a Grand Slam and everyone is inside the top 50."