Striker Gary Birch earned Walsall only their second win in six games with his fourth goal of the season as Bradford City's relegation fears increased.
Birch struck after 76 minutes to earn Walsall an unlikely win after Bradford had squandered three golden second-half chances.
The defeat brought a swift end to Bryan Robson's honeymoon in charge of Bradford.
He had made a winning start to his reign at Bradford with a dramatic win against Millwall last weekend but the defeat at Walsall leaves them rooted in the relegation zone.
Both sides proved to be shot-shy in a dismal opening period when clear-cut chances were few and far between.
Skipper Dean Windass had briefly raised Bradford's hopes when he lashed a 15th minute free-kick just wide from 20 yards.
But, while Windass and his strike partner Andy Gray enjoyed plenty of possession, they struggled to create any real openings.
The best chance to break the deadlock fell to Walsall midfielder Steve Corica, but the Australian international fluffed his big chance.
Corica was released by a neat flick from skipper Paul Merson five minutes from time and raced towards goal pursued by three Bradford defenders.
As he prepared to shoot, Simon Francis got in a vital challenge that put off Corica and goalkeeper Alan Combe completed the rescue act when he beat away the shot with his legs.
Walsall had a major let off of their own eight minutes into the second half when an error by goalkeeper James Walker presented Windass with a golden chance.
A through ball from Tom Kearney caused chaos in the Walsall area and when Walker spilled the ball it fell to Windass who fired wide of an open goal.
That near miss sparked Bradford into their best spell of the game with Gareth Farrelly blazing over the bar from close range nine minutes later.
Jason Gavin then hit the Walsall bar in the 65th minute with a header following a cross from Lewis Emanuel.
Having sucessfully ridden their luck, Walsall made Bradford pay the ultimate price for their failings in front of goal.
Birch was released by a long throughball from Wrack and then lashed an angled drive past Combe.