Wozniacki, seeded third, edged past the top-seeded Stosur 6-2, 4-6, 7-5 in a match that took more than 2 hours. Both women also went to three sets and played for more than 2 hours in winning their semifinals Saturday.
Wozniacki ended up with eight service breaks, including in the final game of the tournament. Stosur grabbed the early third-set lead with a break at love in the first game but Wozniacki returned the break -- also at love -- and evened the match at 3-3.
Stosur had a couple of chances to retake the lead in the ninth game but Wozniacki held in a 10-point game. Wozniacki's first championship point was erased with an ace from Stosur but Wozniacki took the next two points for the title.
Wozniacki improved to 20-11 in WTA finals matches with her second championship of the year. She won in Seoul in September.
Stosur is 3-12 in WTA finals, including a 0-3 record in title matches since she won the U.S. Open in 2011.