Three strokes behind leader Tseng entering the round, Pettersen closed with a 5-under 67 for a two-stroke victory over second-ranked Stacy Lewis.
The 32-year-old Norwegian finished at 20-under 268 for her second LPGA Tour victory of the year and 12th overall. She won the 2011 tournament at Pumpkin Ridge.
Tseng followed her third-round 63 with a 78 to tie for ninth at 12 under. The Taiwanese star is winless in 37 events since the Kia Classic in March 2012.
Lewis, a three-time winner this year, shot a 68.
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