Pawel Abbott set them on their way with his third goal of the season before Keigan Parker opened his Latics account to kill off the below-par visitors.
Carlisle were unbeaten in five away games and they almost went ahead when Scott Dobie was kept out by Dean Brill's save. But Oldham broke through in the 13th minute, with Alan Sheehan bursting forward to tee-up Abbott for a simple close-range finish.
Carlisle threatened an equaliser when Kevan Hurst volleyed off target and Dobie fired against the woodwork from 12 yards.
Oldham doubled their lead after another break forward by the impressive Sheehan, whose low cross was bundled over the line by Parker for his first goal since joining from Huddersfield.
Oldham's first Boundary Park victory in 12 attempts saw them move out of the League One relegation zone.