In 2009, after securing top 10s in the Kraft Nabisco and US Women抯 Open, Pettersen finally broke the duck after two years with victory and a 6th career LPGA title at the CN Canadian Women抯 Open. She won by a convincing 5-stroke margin against the likes of Karrie Webb, Momoko Ueda, Morgan Pressel, Ai Miyazato and Angela Stanford.
 
In 2010, Pettersen missed out on a tournament win but came extremely close on six separate occasions finishing as runner-up each time. These were at the season-opening Honda PTT LPGA Thailand, the Kraft Nabisco Championship and the Bell Micro LPGA Classic and tied for second at the U.S. Women's Open, Evian Masters Presented by Societe Generale and the CN Canadian Women's Open.

In 2011 Pettersen won the Sybase Match Play Championship and the Safeway Classic Presented by Coca-Cola giving her 8 career victories.  She recorded nine additional top-10 finishes including: tied for third at the Wegmans LPGA Championship and the Avnet LPGA Classic; tied for fourth at the CME Group Titleholders; tied for sixth at the Evian Masters; seventh at the Lorena Ochoa Invitational; tied for seventh at the Sime Darby LPGA Malaysia; tied for eighth at the Honda LPGA Thailand; tied for 10th at the Kia Classic and the Walmart NW Arkansas Championship.

2012 saw Pettersen record back to back victories on the LPGA Tour winning The LPGA KEB HanaBank Championship and the Sunrise LPGA Taiwan Championship. It was the sixth consecutive season she crossed $1 million in season earnings.