Adam Smith scored the only goal to earn Chesterfield victory and put them into the Northern Area quarter-final of the Johnstone's Paint Trophy. The 21-year-old, making only his second start of the season, struck his first goal of the campaign with an angled drive in the 19th minute.
It was no more than Oldham deserved after an impressive performance.
Indeed, Janos Kovacs could have added to their lead, but his 41st-minute header was cleared by Neil Wood.
Oldham: Pogliacomi (Legzdins 46), Lomax, Haining, Stam, Tierney, Cywka, Wood (Wellens 75), Taylor, Liddell, Warne (Barlow 64), Hall.
Subs Not Used: Charlton, Trotman.
Chesterfield: Roche, Lowry, Downes, Kovacs, O'Hare, Wiggins-Thomas, Davies, Standing (Nicholson 88), Larkin, Allison, Smith (Jackson 79).
Subs Not Used: Jordan, Hurst, Niven.
Goals: Smith 19.
Att: 2,118
Ref: A Bates (Staffordshire).