The world No. 1 finished at 14-under 274, good for a six-stroke triumph at La Costa Resort & Spa in California.
She entered Sunday's final round with a three-shot lead and turned in another dominating performance. Tseng added the Kia Classic to last week's win at the LPGA Founders Cup and February's victory at the Honda LPGA Thailand.
Sunday's title was the 15th of her career.
Sun Young Yoo claimed second place at minus-8 with a 1-under 71, while Shanshan Feng (67) and Jiyai Shin (74) shared third at 7-under.