Chesterfield's win keeps them in the chase for the play-offs and leaves AFC Wimbledon bottom of League Two.
Armand Gnanduillet stroked Danny Whitaker's cross into the top corner to score his first goal in English football and break the deadlock.
Neil Sullivan saved Drew Talbot's 20-yard drive, but the Dons would eventually fall to a 16th league loss.
Jack Lester sealed it for the hosts, firing a low shot past Sullivan after being set up by Gnanaduillet.
VIEWS FROM THE DRESSING ROOM
Chesterfield manager Paul Cook told BBC Radio Sheffield:
"It was a game that if we didn't win today it would make it a challenge to get in the play-offs.
"Every point is vital and today I told the lads at half-time that this is our season.
"We must remain strong and patient and to the man I felt we did that."
Chesterfield 01 Lee 03 Smith 05 Trotman 06 Hird 31 Cooper 08 Togwell 10 Whitaker (Brindley - 90' ) 23 Randall (Gnanduillet - 46' ) 25 Talbot 34 O'Shea Booked 09 Richards (Lester - 21' Booked ) Substitutes 40 Barrington 17 Brindley 33 Townsend 15 Clay 14 Lester 21 Gnanduillet 22 Wafula AFC Wimbledon 35 Sullivan 06 Mitchell-King 15 Fenlon Booked 31 Meades 39 Bennett 44 Hussey 07 Long (McCallum - 69' ) 27 Sweeney Booked (S Moore - 79' ) 10 Midson (Ajala - 46' Booked ) 11 L Moore 28 Alexander Substitutes 33 Jaimez-Ruiz 03 Cummings 05 Balkestein 08 S Moore 23 Yussuff 38 Ajala 37 McCallum