Former Leeds United trainee Caleb Folan piled the misery on Bradford City with two late strikes as the Spireites came from two down to snatch a dramatic win.
In-form marksman Dean Windass looked to have given City a tonic after their Carling Cup exit in midweek, but his two goals counted for nothing as Roy McFarland's men staged a furious finale.
Spireites skipper Ian Evatt led by example and it was Mark Bower's clumsy push on the Chesterfield centre half which sparked their revival.
Full-back Shane Nicholson coolly despatched the 78th minute spot-kick despite keeper Paul Henderson's full-length dive and a minute later substitute Folan was on hand to slide in the leveller from close range after Evatt had driven the ball back across goal.
City's back four, who had looked comfortable earlier on, now started to crumble and it was no surprise when Folan grabbed the winner a minute from time.
Henderson, who had been impressive under the high ball, was caught out by Jamal Campbell-Rice's deep cross from the left and when he could only claw the ball out Folan side-footed home at the back post.
It was cruel on a City outfit who had lifted their game after a shocking Carling Cup exit at the hands of Notts County in midweek.
After 41 minutes Windass took his goal tally to four in six games with a 25-yard free-kick after Tom Kearney had been impeded.
The in-form frontman curled his effort over an ineffective Spireites wall and there was a also question mark over keeper Carl Muggleton's positioning as he was left rooted to his line.
Ten minutes after the break the Bantams doubled their lead with a well-crafted goal involving on-loan recruit Dele Adebola.
The Coventry man out-foxed the Chesterfield defence with a neat back-heel and Windass powered forward to drive his second past a stranded Muggleton.
At that stage it seemed unlikely that Chesterfield would end their 27-year wait for a victory at Bradford, but Folan's arrival on the pitch and Evatt's presence in the box turned the game.