Mozo holed a 12-foot birdie putt at the 16th hole, taking 3-and-2 victory against Thailand's Moriya Jutanugarn after Jutanugarn couldn't hole an 8-footer to match Mozo's birdie.
The victory gave Spain two points, lifting its total to 13 with two matches still on the course but no other country able to catch the Spaniards.
"We have always played together," Mozo said. "We have always won together. I think coming in, we knew we had that advantage over the other teams, even though we were maybe the underdogs, because of the seedings."
The Spaniards were seeded fifth of eight teams coming into the event.
With Mozo lining up her putt, Japan was the only other country left in the competition with a chance to win. Mozo's victory, however, locked out Japan.