Valiente connected with Omar Ramos' headed on cross just after the break from inside the six-yard box to break the deadlock, which Valladolid held on through the second period to claim their first points of the campaign.
The win marked a turnaround from back-to-back 2-1 defeats by Villarreal and Athletic Bilbao and leaves Getafe still in search of their first win in La Liga this term with only a point from the draw against Almeria to show for their efforts so far.
Valladolid dominated possession and Javi Guerra almost put them ahead in the 10th minute when he headed Ramos' inswinging corner over the bar from close range.
Getafe midfielder Leon then forced a punched save from goalkeeper Diego Marino, with a couple of wayward shots then not troubling the home stopper.
Valiente fired a shot over the bar in the 23rd minute and again three minutes later but it was Guerra who went the closest in the first half when he forced a fantastic save from Getafe keeper Miguel Moya just before the half-hour mark.
After the break, Getafe were caught unawares as Valiente pounced to give the home side the lead. Ramos delivered a testing corner from the left by-line which found Carlos Pena, who headed the ball on to the lurking Valiente to finish from close range.
Some off-target shots from both sides followed before Guerra again tested Moya, who tipped the ball around the post from his 70th-minute effort.
That was the best effort as the game then wound down, with neither side able to break through the other's defences as Valladolid claimed a valuable three points.