Pettersen, who began the day with a bogey, watched as Ochoa just missed a 20-foot putt before calmly making the winner and pumping her fist several times. They both birdied the first playoff hole, with Ochoa make a 15-footer.
'Do it again, Lorena!' someone yelled as she made her way back onto the 18th green.
Pettersen finished with a 1-over 73 to match Ochoa (71) at 11-under 277. Pettersen earned $165,000 for her third victory of the season.
'You know, you've got to play your heart out. It was a nice finish,' Pettersen said. 'There's not a nicer person out there you want to beat.'
The women embraced after both played aggressive golf all day on the hilly Lakeside course at Blackhawk Country Club, then hugged again in the clubhouse later. Pettersen won her second playoff this year.
'She won the playoff the way she should -- being aggressive and with a birdie,' Ochoa said. 'I admire her a lot. She's a very aggressive player and not afraid. ... She has the characteristics of a champion. In my case, I'm going to try to stay ahead. She's pushing me. I like that.'
Pettersen, the Norwegian who held a one-shot lead over Canadian Lorie Kane heading into the final round and was two strokes ahead of Ochoa, had consecutive bogeys on Nos. 9 and 10 to fall three strokes back of Ochoa. Yet Ochoa four-putted for a double bogey on No. 12 as she, Pettersen and Juli Inkster briefly shared the lead at 9 under. That was after Ochoa also bogeyed the 11th.
'I can't believe I won,' Pettersen said while going over her bogeys.
Funny thing is, Pettersen made friends with a 12-week old golden retriever puppy named Bogey. The pooch became her mascot and she saw him each day.
'I can thank Bogey for the trophy,' she joked. 'It's so cute.'
For Pettersen, beating Ochoa had to be sweet: She trails the 25-year-old star from Mexico on every major LPGA Tour list.
Ochoa was trying to win for the fourth time in her last five events, but came up short for the second straight week. She tied for third last weekend in the Navistar LPGA Classic in Prattville, Ala. Ochoa still became the first woman to earn $3 million in a single season, making $101,967.
'I don't care about the money,' Ochoa said. 'I do not like to lose. That hurts me.'
Inkster finished third at 7 under after a 70, while Kane (77) bogeyed the 18th hole and settled for a fourth-place tie with Natalie Gulbis (66).
Nicole Castrale (69) was sixth at 5 under, and defending champion Karrie Webb, still winless this season, shot a 72 to finish at 4 under.
The 26-year-old Pettersen started the day at 12 under after shooting a 65 on Friday and a season-best 64 Saturday for the lowest two-round stretch in the event's 12-year history (129).
But on Sunday, the very hole that helped her gain momentum a day earlier gave her trouble in the final round. She three-putted on No. 9 for bogey after chipping in from 35 yards out for her second eagle on the front nine Saturday.
Ochoa liked her position heading into the final day, despite being two strokes behind and playing in the second-to-last group. She wanted to be aggressive from the first tee shot.
Kane and Pettersen each bogeyed the first hole, while Ochoa calmly made her birdie putt.
Ochoa made a big birdie putt on No. 7 to move to 12 under, with someone in the gallery hollering 'Oy! Oy! Oy!'
A few dozen Hispanics followed Ochoa in the gallery for most of the day, something she has said gives her extra motivation.
'Nice shot, Lorena!' screamed 4-year-old Ariana Molera.
Molera, of nearby Martinez and watching with parents Jerry and Jonnell, received a wave from the Mexican star.
'Vamos, Lorena!' one man yelled later -- 'Let's go, Lorena!' in Spanish. Ochoa also gave the thumbs-up sign to a Hispanic fan.
After finishing up on No. 8, Ochoa handed a ball to another young girl cheering her name.
Maria Hjorth, the winner last weekend in Alabama, tied for eighth at 3 under along with Inbee Park
Copyright 2006 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.