The hard-serving 21-year-old from Thornhill, Ont., beat top-seeded Janko Tipsarevic of Serbia 6-7 (4), 7-6 (4), 7-6 (4) in a serve-dominated final of the Chennai Open on Sunday.
Fourth-seeded Raonic hit 35 aces in a marathon match that lasted three hours, 16 minutes and didn't feature a break of serve.
"It is an awesome feeling," said the 21-year-old Raonic, who won all 48 of his service games during the week to become the first player to win a tournament without dropping serve since Swiss star Roger Federer at the 2008 grass-court tournament in Halle.
Raonic dropped only four points on serve in the first set and had four chances to break in the fourth game before Tipsarevic stole it on a tiebreaker.
"Tipsarevic took it away in the first set," Raonic said. "But I took my opportunities in the second and third."
Raonic established a 4-1 lead in the second-set tiebreaker before levelling the match on his second set point. He had to save break points early in the decider but dominated the tiebreaker with his serve.
"My serve is a big factor in my game ... in 99 per cent of my matches," said Raonic, who averages a consistent 200 kilometres per hour on his first serve. "My job is to take care of my serve."
The ninth-ranked Tipsarevic has now lost six-of-eight ATP finals in his career.
"Guys like Milos are special players," Tipsarevic said after his first match against the Canadian. "It was a great game of tennis. Nobody knew till the end who would win.
"Unluckily for me it was I who lost. It was just a matter of a few points here and there. Hopefully the next time I will get the better of him."
The Canadian is 2-1 in ATP World Tour finals, claiming his first title in San Jose last February. He followed that up by finishing runner-up to American Andy Roddick in Memphis a week later.
Raonic rose from No. 156 in the rankings to a career-high 25th last season before moving down slightly to his current No. 31. He won the ATP Newcomer of the Year award last year.
Raonic heads to Kooyong, Australia, to play in an exhibition event, a tuneup to the Australian Open in Melbourne, which begins Jan. 16.
— With files from The Canadian Press.