Simon Grayson's side climbed to sixth in the table thanks to first-half goals from Stuart Beavon and Kevin Davies, but they were made to work for their victory at Deepdale.
Oldham were the better side in the opening 45 minutes but could not make their advantage pay, and although James Tarkowski pulled back a late goal, they were unable to win a point.
Lee Johnson's men started brightest and Sidney Schmeltz had an early chance on goal for the visitors.
Preston claimed the lead after 13 minutes though, as Joel Byrom's free-kick was headed in by Beavon.
Byrom struck his effort straight at the wall and Beavon reacted cleverly, flicking beyond the stranded Mark Oxley in the Oldham goal.
The visitors continued to press for an equaliser and were desperately unlucky not to get one as Tarkowski saw a header cleared off the line, while another effort was desperately hacked away in the aftermath.
Preston's second goal came when Davies was fouled in the area by Australian James Wesolowski.
It was a needless foul and former Bolton Wanderers striker Davies tucked away the spot-kick expertly as Preston took a two-goal lead at the break.
Scott Laird and Davies missed chances to seal the game for Preston and with seven minutes left, Tarkowski gave Oldham a lifeline when he headed in a corner.
But Preston hung on to win all three points and maintain their unbeaten run in League One.
