Steve Claridge clinched Bradford's third away win of the season.
He produced a typical poacher's finish midway through the second half, tucking away a rising shot following a driving run from Ben Muirhead.
Vale went close when Mark Bower was almost pressured into putting the ball into his own net.
Bradford goalkeeper Donovan Ricketts, returning from an eight week absence with a broken foot, saved a piledriver from George Pilkington.
Port Vale: Goodlad, Pilkington, Collins, Dinning, Bell (Husbands 81), Birchall, Sonner, Cummins, Cornes (Lowndes 72), Paynter, Mulligan.
Subs Not Used: Brain, Innes, Rowland.
Bradford: Ricketts, Taylor, Wetherall, Bower, Edghill (Holloway 84), Muirhead, Schumacher, Crooks, Petta (Emanuel 58), Claridge, Windass.
Subs Not Used: Cooke, Cadamarteri, Kearney.
Goals: Claridge 64.
Ref: P Robinson (E Yorkshire).