Pettersen began Sunday with a four-shot lead but saw that wiped out when Solheim Cup team-mate Munoz picked up four birdies in her first 12 holes at Sunrise Golf and Country Club.
However, the Spaniard then bogeyed the par-five 13th as Pettersen birdied, and, when Pettersen also picked up a shot at the next, she was suddenly enjoying a three-shot cushion once more.
Another bogey from Munoz on the 16th effectively ended her chances and world number two Pettersen completed a 69 in style with a birdie on the 18th to finish nine under, five shots ahead of Munoz.
Sweden's Caroline Hedwall claimed third place on two under after matching Munoz's final round of 70, with South Korea's Eun-Hee Ji the only other player to finish in red figures.
"It feels great to come here and defend my title and play as well as I did," Pettersen said after her fourth win of the season and 14th career LPGA Tour victory.
"It was very tough out there. Since the very first shot on Thursday, the conditions gave us a very big challenge. Today, Azahara gave me an even bigger challenge.
"She played really good on the front nine - well, she played really good all around. I think I can almost thank her for keep pressing and keep pushing me because I just had to keep staying aggressive and try to make birdies."