Sorenstam won for the second time in 2008 with a par on the first extra hole after she and Creamer finished at 8-under-par 275 in regulation.
Sorenstam, who had led entering the final round, closed with a 1-under 70. Creamer shot a 69.
"I'm just fortunate that this time it was my turn, and I'm going cherish this moment," Sorenstam said. "I felt like I played well the whole week. This is a big tournament on our schedule, and it meant a lot to me to come down the stretch there and hit some really crucial shots and finish strong."
The Swedish star trails only Kathy Whitworth (88) and Mickey Wright (82) in all-time tour victories.
Sorenstam collected $300,000.