WILLIAMSBURG, Virginia, May 5, 2013 (AFP) - Pettersen hadn't made a bogey all day, notching four birdies in a four-under par 67 to join overnight leader Kerr on 12-under par 272.
Kerr, a winner at Kingsmill in 2005 and 2009, had four birdies and two bogeys in a 69 to maintain a share of the lead and force the playoff.
Kerr said she was motivated by having family in the gallery.
"It's the first time my dad got to see me win, so it's really special for me," said Kerr. "I wasn't going to lose, not today, not with my dad here."
Thai teenager Ariya Jutanugarn, who had seized the first-round lead on Thursday with a scintillating 64, finished strong with a 66 to share third on 274 with South Korean Lee Il-Hee, who carded a 67.
Americans Angela Stanford and Stacy Lewis were tied on 275, Stanford with a final-round 69 and Lewis a 70.
World number one Park In-Bee of South Korea finished alone in sixth place after a 67 for 276.
It was the second straight year the Kingsmill Championship was determined in a playoff. In 2012, Shin Ji-yai beat Paula Creamer in a nine-hole epic that finished on Monday after darkness halted play.
On Sunday, Kerr and Pettersen played the 18th hole for both playoffs.
Kerr missed a five-foot birdie attempt on the first extra hole to force the second playoff hole.
The American hit her second shot to about 20 feet from the cup while Pettersen's second shot rolled off the back of the green. Pettersen's third halted 15 feet short of the pin.
Kerr tapped in on her second put for her 16th career LPGA Tour title.
Leading final-round scores on Sunday at the LPGA Kingsmill Championship (x-won playoff at 2nd hole, USA unless noted, par-71):
272 - x-Cristie Kerr 66-71-66-69, Suzann Pettersen (NOR) 68-69-68-67
274 - Ariya Jutanugarn (THA) 64-71-73-66, Lee Il-Hee (KOR) 69-69-69-67
275 - Angela Stanford 68-68-70-69, Stacy Lewis 68-68-69-70
276 - Park In-Bee (KOR) 68-72-69-67
279 - Ryu So-Yeon (KOR) 67-71-73-68
280 - Gerina Piller 72-71-71-66, Anna Nordqvist (SWE) 70-72-70-68, Sandra Gal (GER) 68-69-73-70
281 - Paula Creamer 69-70-74-68, Choi Na-Yeon (KOR) 69-73-70-69, Amy Yang (KOR) 69-72-71-69, Caroline Hedwall (SWE) 68-73-70-70, Katie Burnett 68-70-71-72
282 - Alison Walshe 69-70-74-69, Chella Choi (KOR) 70-73-68-71, Lizette Salas 72-71-65-74
283 - Seo Hee-Kyung (KOR) 71-71-74-67, Giulia Sergas (ITA) 74-68-70-71, Feng Shanshan (CHN) 69-69-73-72, Jane Park 68-71-72-72
284 - Julia Boland (AUS) 73-71-70-70, Tseng Ya-ni (TPE) 69-72-71-72, Karrie Webb (AUS) 70-71-70-73, Mo Martin 68-72-70-74
285 - Lee Jee-Young (KOR) 68-74-74-69, Brittany Lincicome 75-69-71-70, Yoo Sun-Young (KOR) 71-73-69-72, Jenny Shin (KOR) 71-72-68-74