A break in each set was enough for the seventh seed to claim his third title of the year and seventh of his career.
“I'm just happy. There's nothing else I can say, honestly," the 26-year-old told reporters.
"I'm just happy and I'm humbled to have that trophy in my hands, and especially to win here, my first Masters 1000.
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"I always like this tournament. I have played it quite a few times and always thought this can be maybe one of the first ones, and it is the first one."
Dimitrov did not drop a set all tournament, the first player to do so at a Masters 1000 tournament since Novak Djokovic's 2007 win at Miami.
He was almost impregnable on serve, winning 52 of his 53 service games.
"Going to the (U.S.) Open, it's for sure a lot of positivity with it," said Dimitrov, a semi-finalist at the Australian Open in January.
"But the most important thing now is just to stay grounded, keep on doing the same work, believe in myself, and just prepare the best way that I can for the Open."
Both players were in their maiden Masters 1000 title match but Dimitrov showed more poise than his 22-year-old opponent, saving a pair of early break points to set the tone.
Kyrgios's 31 unforced errors comfortably outstripped his 21 winners, the combustible Australian unable to find the magic he produced in his quarter-final win over Nadal.
But he was thrilled with his run to a first final of the year, having been jeered by the crowd three weeks ago at the Citi Open in Washington D.C. when he retired from his match with a shoulder injury.
"Looking back from where I was... I would have never thought I would have had my first Masters 1000 event final," he said.
"So I'm pretty happy with the result. From where I was to here, it's just been amazing.
"I lost today but I feel great. I feel great where I'm at right now ... I'm pretty excited for the U.S. Open."
The U.S. Open starts Aug. 28.
(Reporting by Andrew Both in Cary, North Carolina and Jahmal Corner in Los Angeles; Editing by Ian Ransom)
