'I was like, `Wow! It happened,'' she said of her first victory, which came Sunday when Jee Young Lee missed a 2-foot par putt on the third extra hole in the Michelob Ultra Open and Pettersen calmly made hers.
The win came in Pettersen's 82nd LPGA Tour event, and made her the first Norwegian ever to win on the premier women's tour.
When Pettersen's putt fell, she pumped her right fist in celebration, then doubled over trying to create a private moment to savor before she was doused with beer.
'It feels special, I must say,' she said. 'Well, I didn't expect to win.'
Four stokes behind Lee to start the day, Pettersen shot a 3-under 68 to match Lee (72) at 10-under 274, avoiding the bogeys that plagued Lee and most everyone else as a stiff wind changed the course.
'The wind was good for me,' Pettersen said, because she felt she was striking the ball so purely, it didn't matter. 'It made it a little difficult for the other ones.'
Also good was Pettersen's recent history of near misses, including two this year. One came despite her best effort, the other was as demoralizing as the way Lee lost.
Second twice in her first seven events this year, the 26-year-old closed with a bogey-free 66 in the Safeway International in March, but lost when top-ranked Lorena Ochoa birdied four of the last five holes. Pettersen then blew a three-shot lead with a bogey-double bogey-bogey-par finish at the Kraft Nabisco -- a major -- the next week.
Those experiences, she said, helped her get through Sunday's tension.
'Even the playoff, I don't think my heart rate was much more than when I played the regular 18 holes,' Pettersen said. 'It could possible be the experience I had a month ago.'
This time, she let the opponent flinch.
Both players parred the par-4 18th on the first two extra holes, and Lee seemed to have the upper hand the third time around when she hit her approach to about 12 feet while Pettersen's ball rested against the high grass at the edge of the fringe.
'I told my caddy, `She's going to make this,'' Pettersen said.
Lee was thinking the same thing.
'Unless Pettersen makes the putt, I think I have a chance to win,' a still distraught Lee recalled thinking when they reached the green for the 75th hole.
Pettersen's putt rolled just past the cup on the right side, leaving 1 1/2 feet, and Lee's attempt at the victory missed to the right, leaving a short putt for the tie.
Lee, seeking her second career victory, quickly went to knock hers in, seemed to rush and it skated by on the right as the crowd gasped and she looked up, astonished.
'I just wanted to putt it and not have to wait,' she explained through an interpreter between calming deep breaths and disbelieving sighs. 'Frankly speaking, I think I played well enough (to win), but I think I gave it away.'
She did, at the end, but Pettersen made it possible with a sterling round.
The swirling, gusting wind played havoc with most players, often causing them to rethink their club selection. Pettersen was the only player of the 77 in the field to go through Sunday's round without a bogey, and only one player scored better.
It all only added to the thrill of finally breaking through.
'I mean, you've been dreaming of this since you're a kid,' she said. 'This is the league you want to play in, against the best players and on a course like this.
'You can't get much better.'
Not so for Lee, who was flawless in a course record-tying 63 on Saturday, but had four bogeys and three birdies in her closing 72. The last birdie came following a sand save immediately after a bogey at No. 14 briefly gave Pettersen a one-shot lead.
It was the only time she led all day until the final putt.
Lee also missed putts from inside 5 feet on the 10th and 14th greens.
Sarah Lee, who started the day one shot off the pace, finished three strokes back after a 74. Stacy Prammanasudh, who matched Pettersen's 68, and crowd favorite Paula Creamer (72) shared fourth. Angela Stanford had the day's best round, a 67.
The victory, worth $330,000 from the purse of $2.2 million, guaranteed Pettersen a spot in the November ADT Championship as the winner of one of 10 $2 million events.