CANADA, 7 Jun 2015 (AFP) - Pettersen closed with a three-under 69 at the Whistle Bear Golf Club course to snap a two-year winless drought and become the first European winner in the tournament's short history.
"It was a tougher day today. But I finished strong," Pettersen said. "I felt I played good golf this week."
Pettersen birdied two of the final three holes in the fourth round to edge American Brittany Lang, the event's inaugural champion who fired a final-round 65. Pettersen finished the tournament at 22-under par 266.
Park Hee-Young won in 2013 and her South Korean compatriot Park In-Bee claimed the title last year.
The tour's next stop is Harrison, New York, for the Women's PGA Championship where world number two Park In-Bee will try to defend her major title starting Thursday.
Colombia's Mariajo Uribe, who was seeking her first career win, finished alone in third at 270 after capping her week with a 72.
China's Feng Shanshan fired a 67 to finish in a group of four players who shared fourth on 272.
The 34-year-old Pettersen has looked good since returning from a left shoulder injury that forced her to pull out of a pair of tournaments in April.
"There have been some tears and pain. I felt like I was bouncing my head against the wall with the injuries and such," she said.
Pettersen came into the final round after going bogey free through the first 54 holes.
She got off to rough start Sunday with her first two bogeys of the tournament in the initial five holes, but then settled down with back-to-back birdies to close out her front nine.
She finished with five pars, one bogey, two birdies and an eagle, on the par-five 12th, on the back nine.
"I made some stupid mistakes early, but I kept digging deep," she said.
Cristie Kerr had a share of the lead as late as the ninth hole, but bogeyed four in a row to close her round with a 73 and finished tied with Feng.
Lang, who had five birdies and a bogey through 14 holes, caught fire with a 14-foot birdie putt at 15. She also birdied the 16th to join Pettersen and Kerr in the lead.
Lang drained her third straight birdie at the 17th, to grab the lead at 21-under.
Shortly after Lang parred the 18th, Pettersen tapped in a birdie at the par-five 16th to tie Lang at minus-21.
Pettersen rolled in a six-footer for birdie on 17 to move ahead by one. She two-putted the 18th for par and the victory.
Park In-Bee shot four-under 68 to finish tied for 11th at 13-under-par 275.
Leading final-round scores on Sunday from the US LPGA Tour Manulife Classic (USA unless noted, par-72):
266 - Suzann Pettersen (NOR) 66-65-66-69
267 - Brittany Lang 65-68-69-65
270 - Mariajo Uribe (COL) 65-66-67-72
272 - Cristie Kerr 63-69-67-73, Ryu So-Yeon (KOR) 68-69-66-69, Jacqui Concolino 71-64-68-69, Lee Min-Jee (AUS) 69-66-70-67
273 - Feng Shanshan (CHN) 67-67-72-67
274 - Lee Il-Hee (KOR) 66-72-66-70, Kim Hyo-Joo (KOR) 66-67-72-69
275 - Park In-Bee (KOR) 69-68-70-68, Julieta Granada (PAR) 65-69-69-72, Jenny Shin (KOR) 67-70-70-68, Charley Hull (ENG) 68-68-70-69