The Spireites lost 3-0 at Meadow Lane.
John Pemberton's unbeaten record as Chesterfield's Caretaker Manager came to an end over the weekend.
Three unanswered second half goals resulted in the Spireites' first defeat since New Years Day.
However, it could've all been different for the visitors, who missed a golden opportunity to take the lead in the first half.
David Buchanan was brought down by Richard Brindley in the hosts' penalty area five minutes before the break, resulting in a spot-kick for Pemberton's men.
Striker Scott Boden stepped up to take it, but his tame effort was saved by Ross Fitzsimmons.
Enzo Boldewijn punished the Spireites seven minutes into the second-half, as he produced an unstoppable effort to leave Shwan Jalal with no chance.
Tom Denton nearly got an equaliser for Chesterfield shortly afterwards, but his volley crashed against the crossbar.
County doubled their advantage just before the hour mark through Kyle Wootton's diving header, and the points were all but secured in the 76th minute as Wootton tapped in his second goal of the evening.
Speaking afterwards, Pemberton expressed his disappointment at not taking the lead in the first half;
"It was a big moment in the game for us. It's a kick in the teeth that we couldn't put that one away as goals change games.
"It wasn't a 3-0 game, but it's happened to us and we need to recover now.
"They're a good footballing side and I think the big difference was how well they used the ball.
"It's up to us now to put this behind us and get a result on Saturday."
The loss leaves Chesterfield 21st in the National League, three points from safety.