Danny Whitaker struck a penalty for Chesterfield to give his side the edge in the first leg of the Johnstone's Paint Trophy Northern final.
Scott Boden opened the scoring for the home side when he converted a James Hurst cross before Robbie Simpson's spectacular equaliser for Oldham.
Whitaker then scored from 12 yards before Oldham striker Shefki Kuqi saw his spot-kick hit the crossbar.
The sides meet again in the second leg at Boundary Park a week on Monday.
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Chesterfield manager John Sheridan told BBC Radio Sheffield:
"You wouldn't think we were bottom of the league the way we we've gone about trying to win the game against a very good footballing side.
"To come out of the game with an advantage going into the second leg is very pleasing for us and that's what we wanted.
"The work ethic and desire was different class and we created some really good chances."
Oldham Athletic manager Paul Dickov told BBC Radio Manchester:
"It's going to make for a really good game as they've got the problem of do they come and defend their lead, or do they come and attack?
"I'm disappointed with the goals we lost as it was basic things we didn't do right and we got punished.
"If we take the attacking side into the game in 10 days' time then I'm sure we'll be doing OK."