This week's tournament at Club de Golf Mexico is the penultimate event of the season.
An eagle at the par-five second hole was followed by four birdies with two bogeys as Ciganda built a 13-under par total of 275.
That put her two clear of England's Jodie Ewart Shadoff, France's Karine Icher, Australian Sarah Jane Smith and Americans Austin Ernst and Angela Stanford.
Ernst, who took a one-shot lead into the final round in pursuit of a second career crown, carded a one-under par 71.
Smith, a Queenslander seeking her first title, had shared the first-round lead with Ciganda and led outright at the halfway stage. She closed with a two-under 70, while Shadoff seized her slice of second with a 67 and Stanford and Icher both signed for 69s.
Ciganda started the day one stroke behind Ernst. That was nothing like the five-shot deficit she made up in October to capture her first LPGA title in the Korea LPGA Championship in Incheon with a playoff victory over American Alison Lee.
That made the 26-year-old from Pamplona, a three-time winner on the Ladies European Tour, the third European winner on the LPGA tour this year, following Sweden's Anna Nordqvist and Germany's Caroline Masson.
This week's tournament at Club de Golf Mexico is the penultimate event of a season that concludes next week with the Tour Championship in Naples, Florida.