Shin had back-to-back birdies at Nos. 14 and 15 to provide enough space to hold off Tseng, whose 7-under 66 was the round of the day Sunday. Shin was 18-under 274 for the tournament while Tseng ended up at 16-under.
Lydia Ko, a 15-year-old amateur, finished third at 14-under after a final round of 3-over 76. Ko entered the final round tied with Shin for the tournament lead.
Shin and Ko were six strokes up on third-place Beatriz Recari and Tseng was in a group eight behind the leaders going into the final round. Recari had a 2-under 71 Sunday and ended up tied for fourth.
Tseng had a first-hole bogey and then ran off three consecutive birdies. She added an eagle at the par-5 sixth hole and had three birdies on her second nine. Two of those came on par 3s.
Ko opened with a double bogey and was 3-over after two holes. She had birdies at Nos. 4 and 5 but was 2-over on the second nine in falling well back of Shin.
Shin birdied the first hole and used consistent play -- she had 13 pars Sunday -- to keep ahead of Tseng. She did have bogeys at 5 and 12 but countered those with her birdies at 14 and 15.
The Women's Australian Open victory marked Shin's 37th professional win and 11th on the LPGA Tour.
The event was the opening tournament in the 2013 LPGA schedule.