The Spanish duo won the kayak double 500-meter race, handing Ronald Rauhe and Tim Wieskotter of Germany their first loss in seven years.
The top two teams were separated by just .091 of a second at the finish line after the Germans had gotten off to a slow start. Rauhe and Wieskotter had been looking for their second straight Olympic title.
"What can I say, it wasn't going to last forever," Rauhe said.
In another upset, Australia's Ken Wallace left Adam van Koeverden of Canada with his second disappointment in as many days.
Van Koeverden had been favored to win in the single kayak races over both 500 and 1,000 meters. He finished a shocking eighth over 1,000 meters Friday and settled for the silver medal in the 500 Saturday behind Australia's Ken Wallace. It was the second medal for Wallace, who won the bronze in the 1,000-meter race.
"I have not dealt with failure before," van Koeverden said. "In the last 24 hours, I have certainly been dealing with it."
Other winners Saturday included Maxim Opaley of Russia in the single canoe, Inna Osypenko-Radomska of Ukraine in the single kayak, Katalin Kovacks and Natasa Janic in the double kayak, Meng Guanliand and Yant Wenjun in the men's double canoe.