Caolan Lavery marked his debut for the Spireites with the winning goal midway through the second half to strengthen Chesterfield's play-off bid.
The result means that Chesterfield have now lost just once in their last eight league games.
Lavery, signed on loan from Sheffield Wednesday on transfer deadline day, lined-up alongside Armand Gnanduillet in attack with fellow deadline day recruits Mani Dieseruvwe and Mark Duffy among the substitutes.
The new-look strike-partnership threatened to carve out an early chance when Lavery's low cross just evaded Gnanduillet, who was running in at the far post.
Sam Clucas had Chesterfield's first effort on goal in the tenth minute when he received a lay-off from Jay O'Shea inside the area and fired in a shot which was beaten away by keeper Roy Carroll.
Chesterfield were caught on the break with Balint Bajner making a strong run before drilling a low shot narrowly wide of Tommy Lee's left-hand post.
Clucas put another effort on target, this time meeting Dan Jones' free-kick with a header which was comfortably saved by Carroll.
The Spireites had a real let-off in the 14th minute when Bajner had a close-range shot saved by Lee and then stabbed the rebound wide.
Lee was called into action again shortly afterwards when he used his legs to keep out Curtis Thompson's shot at his near post.
After weathering a spell of pressure, Chesterfield threatened to score on the break when O'Shea ran from his own half before slipping the ball to Lavery on the right-hand side of the area and the debutant's low shot was touched wide by Carroll. Gnanduillet headed wide from the resulting corner.
Jimmy Ryan then tried a 20-yard shot which failed to pose too much of a problem for Carroll.
The lively Bajner was in the thick of the action again when his deflected shot fell into the path of Liam Noble and Lee had to get down smartly to make a brave block.
Blair Adams, who scored in the 1-1 draw between the two sides at the Proact in September, had a long-range effort saved by Lee.
Lavery looked certain to score in the closing stages of the half when he met Gnaduillet's knock-down from O'Shea's free-kick, but Carroll somehow kept out his close-range effort.
O'Shea created space for himself inside the area soon after the re-start before firing over.
After Bajner, had a shot deflected wide, the Spireites enjoyed a good spell.
Gnanduillet headed off-target from a Ryan cross and O'Shea's low shot was saved by Carroll before the breakthrough came.
Chesterfield profited from some good fortune when an attempted clearance from Haydn Hollis saw the ball strike Lavery (67) and then loop high into the air, over Carroll and into the net.
A few minutes later, Lavery was taken off and replaced by another recent recruit, Byron Harrison.
Within the space of a few minutes, Tendayi Darikwa and Sam Hird were booked.
Harrison threatened to find a way through when Clucas played the ball into the area, but Carroll was smartly off his line to claim.
After O'Shea put a free-kick well over, manager Paul Cook made a second change with Dieseruvwe taking over from Gnanduillet.
Five minutes of stoppage time was added, but the home side never threatened to equalise.
Notts County: Carroll, Dumbuya, Adams, Smith (Jones 65), Mullins, Hollis, Hayhurst, C Thompson, Noble (Thomas 76), Woolery, Bajner (G Thompson 73).
Unused substitutes: Pilkington, White, Daniels, Edwards.
Chesterfield line-up: Lee; Darikwa, Hird, Evatt, Jones; O'Shea, Morsy, Ryan, Clucas; Lavery (Harrison 70), Gnanduillet (Diesreuwve 86).
Unused substitutes: Chapman, Humphreys, Raglan, Duffy, Banks.
Chesterfield: Lavery 67
Referee: Keith Stroud
Attendance: 6,649 (1,838 away fans)