Scunthorpe should have opened the scoring after only three minutes when a cross from the left by Kevan Hurst was met by Paul Hayes from close range, but he managed to shoot wide when it was easier to score.
Ian Baraclough was booked for a foul after 17 minutes and two minutes later Billy Jones the Preston right-back limped off injured to be replaced by Darren Carter.
Jack Cork hit a 15-yard left-foot shot which went wide of the keeper's left-hand post and Jim Goodwin hit a 20-yard left-foot shot which went over the bar after 40 minutes.
Sean St. Ledger made a mistake in the Preston half after 42 minutes and Martin Paterson ran through to score with a 12-yard right-foot shot into the bottom middle of the net from the right-hand side of the penalty box, the only goal of the game and his tenth league goal of the season.
Simon Whaley hit the post for Preston in the last minute of the first half when good work by Paul Gallagher and Neil Mellor found Whaley and he hit a 15-yard right-foot shot against the post.
Carter was booked after the half-time whistle when he argued with the referee about a corner.
Paterson had another shot saved by Preston keeper Andy Lonergan, before Matt Hill was booked for a foul on Matthew Sparrow and Gallagher forced a save in the 63rd minute.
Mellor and Gallagher had near misses and then Sparrow had a 25-yard left-foot shot saved by Lonergan.
Cliff Byrne was booked for a foul in the 87th minute.
Paul McKenna, the Preston captain, hit a 35-yard right-foot shot over the bar with one minute to go and in the last minute Byrne lost his head, fouling Carter off the pitch and receiving his second yellow card, followed by a red card.