Girona travelled having only lost once across their last five games, but Valladolid made a hugely positive start at the Estadio Municipal Jose Zorrilla, almost taking the lead through a Cyle Larin header that went just wide of the post.
The hosts pressed on regardless, and got their deserved breakthrough midway through the first half, when Gonzalo Plata brilliantly picked out Monchu with a low cross, which resulted in the midfielder finding the bottom corner to score only his third goal of the season.
Though naturally stunned, Girona weren’t without their own major chances in response, and the first of them fell to Javi Hernández, who forced Jordi Masip into a good save from outside the area.
Paulo Gazzaniga was also a busy man in between the sticks, keeping his team in the game when he denied Selim Amallah by tipping his well-struck effort around the post.
Seeking his first away goal since September, Arnau Martinez also blew a huge chance to level as the interval loomed, somehow spurning a glorious chance by putting an effort just wide of the post from 10 yards out.
Larin then had another opportunity to add to his five league goals this season following the restart, but his powerful header was turned over the bar by a great Gazzaniga save.
Soon after that flashpoint, Valery Fernandez became the latest Girona player to miss from close range as he failed to meet a low cross, allowing Iván Fresneda to make a last-ditch tackle.
The hosts had failed to keep a clean sheet in their previous eight games, but remarkably, they limited Girona to very few chances to comfortably see out the game.
A second win for Valladolid in their last three games takes them up to 14th in LaLiga, while Girona remain stuck in 10th, having missed the opportunity to close a nine-point gap on the European places.