Preston opened the scoring with the first chance after eight minutes.
Jon Parkin found Chris Sedgwick who beat Charlie Lee on the right wing and crossed the ball to Neil Mellor, whose low close range shot went into the middle of the net.
After 13 minutes Richard Chaplow found Callum Davidson. His left-wing cross found Jon Parkin at the far post and his effort was saved by Peterborough goalkeeper Joe Lewis.
A minute later Lewis confidently claimed an inswinging corner by Preston left-winger Ross Wallace.
Barry Nicholson sustained a serious leg injury after a foul on George Boyd and was stretchered off and substituted by Darren Carter after 26 minutes.
Referee David Webb booked Nicholson as he headed off to the dressing room.
Preston made it 2-0 after 30 minutes when Mellor put Billy Jones clear and the right-back scored from inside the penalty area high into the middle of the goal.
Tommy Rowe replaced Posh left-back Lee after 33 minutes.
Carter and Davidson were booked for fouls on Paul Coutts after 38 minutes.
Preston goalkeeper Andrew Lonergan saved a Coutts cross after 44 minutes.
Gabriel Zakuani fouled Mellor and was booked just before half-time.
A Boyd cross was saved after 51 minutes and Lee Frecklington replaced Toumani Diagouraga two minutes later.
After 60 minutes a Wallace cross was saved and after 64 minutes a Chaplow centre was saved.
Paul Parry replaced Mellor after 65 minutes. Sedgwick had a shot saved after 68 minutes.
Dominic Green replaced Shaun Batt after 72 minutes.
Frecklington had a shot saved and then Chris Brown replaced Parkin after 76 minutes.