Kenneth Zohore and Chris Maxwell challenge for the ball
Cardiff City failed to move back into the Championship top two as they were beaten for the third successive game.
Alex Neil's visitors made it nine games unbeaten in a contest they shaded before skipper Tom Clarke bundled home their winner in the last minute.
The Bluebirds were miles short of their best and can now only look on when leaders Wolves face second-placed Bristol City on Saturday.
Preston rise to seventh and are just a point outside the play-off berths.
Cardiff had never lost three successive games in Neil Warnock's tenure as manager before this game, but he endured a miserable night where he presided over his 1400th game as a manager.
The decisive moment of the match came in the last minute of normal time, with Clark firing home from three yards after Neil Etheridge saved a point-blank header from a corner.
The visitors were the better side in the first period, though that is a relative statement after a stale 45 minutes that were extremely short on quality. The hosts, especially, looked a pale imitation of the side that until recently had been sweeping all before them in the Championship.
In a half without a shot on target, Preston's best opportunity came when Nathaniel Mendez-Laing came within a few inches of conceding a penalty after a foul right on the edge of the area, before the visitors saw another claim waved away after Lee Peltier looked to have handled the ball.
Jordan Hugill also hooked over, with Lee Tomlin and Joe Ralls missing half chances for the hosts who were missing the injured Aron Gunnarsson and could only include talisman Junior Hoilett among their substitutes.
Tomlin angled a header towards goal shortly after the break, with Chris Maxwell finally saving the first effort on target in the match, but the second half continued like the first, with scarce incident and lots of long balls.
Ninth-placed Preston looked more than comfortable, but seemed to have squandered their best chance with 15 minutes remaining when Neil Etheridge palmed away Tom Barkhuizen's low effort with Bruno Ecuele Manga tackling Hugill and preventing what would have been a tap-in.
However, Clarke had the final say as the Bluebirds' miserable festive period continued, despite sub Rhys Healey forcing Maxwell to save at the death.
Source: bbc.com