Her left shoulder finally pain-free and her hard work with new instructor Butch Harmon showing, the 34-year-old Norwegian ended up putting it all together at the Manulife LPGA Classic.
''I hope I didn't peak one week early,'' Pettersen joked Sunday after winning her 15th LPGA title and first since October 2013. ''But this is just a start. This is what I've been working for. I'm starting to feel that the process is kind of coming together. This is a start of a big summer.''
Pettersen birdied two of the last three holes, closing with a 3-under 69 in windy conditions for a one-stroke victory over Brittany Lang at Whistle Bear Golf Club.
Pettersen blasted out of a greenside bunker to 2 feet on the par-5 16th to set up a birdie that tied Lang for the lead, then hit a 5-iron to 8 feet for another birdie on the 191-yard, par-3 17th. The European Solheim Cup star parred the par-4 18th, hitting her long first putt to a foot.
After playing bogey-free in opening rounds of 66, 65 and 66, Petersen dropped strokes Sunday on Nos. 2 and 5. She rallied with birdies on Nos. 8-9, eagled the par-5 12th, and made a bogey on the par-4 13th.
''I felt I played some really good golf this week,'' Pettersen said. ''I was pretty flawless through three rounds and broke that effort pretty quickly with a couple of bogeys, but I managed to get my head together and play some good golf. I played aggressive and it was a good day on the golf course.''
Pettersen finished at 22-under 266. She ended a 35-event victory drought and is projected to jump from 10th to fifth in the world ranking.
''I went to see Butch and I have only good things to say about Butch,'' Pettersen said. ''He's been a great inspiration to me to take my game to a new level. He definitely has the belief. He's no sugar-coater. He gives me what I need every single time.
''What we've done so far is good and this is hopefully just a start. But it's nice to kind of see the results. When you do changes, I can feel the difference in what's happening and what's going on.''
Lang, the winner of the inaugural tournament in 2012 at Grey Silo, finished with a 65. She birdied Nos. 15-17 and closed with a par.
''I'm going to take nothing but positives away from this week,'' Lang said. ''It was fantastic golf with three majors coming up. But the competition out here, it's unbelievable. It's really hard to win nowadays and it's great, it's great for women's golf. The girls are just, there's so much talent, so much depth.''
Colombia's Mariajo Uribe was third at 18 under after a 72.
Cristie Kerr bogeyed the final four holes for a 73 to drop into a tie for fourth at 16 under.
Top-ranked Lydia Ko tied for 27th at 10 under after a 71.