Non Stanford won the fourth round of the World Series event in Madrid - the Briton's first victory of the season.
The 24-year-old finished 26 seconds ahead of Germany's Anne Haug, with British teammate Jodie Stimpson finishing in third place.
The championship leader, Gwen Jorgensen from the United States, finished in fourth place.
"That was really hard," said Stanford. "I thought I had gone off too hard in the run but I held it together."
Stanford, from Swansea, missed races in Auckland and Yokohama, but was runner-up in San Diego in April. This result lifts her to fifth in the world rankings.
