Richard Logan scored twice for Posh, whose victory leaves Notts County in the Division Two relegation zone. Logan put Peterborough two-up after Curtis Woodhouse's header had opened the scoring on 10 minutes.
Paul Riley netted goals either side of half-time to level, but David Farrell marked his 300th game for Posh by restoring their lead with a volley.
Logan got his second from point-blank range and substitute Andy Clarke robbed Nick Fenton before firing in the fifth.
Peterborough: Tyler, Gill, Rea, Arber, Williams, Farrell, Thomson, Woodhouse, Legg, Logan, Willock. Subs: Andy Clarke, Newton, Fotiadis, Burton, Pullen.
Notts County: Mildenhall, Fenton, Barras, Richardson, Nicholson, Baldry, Caskey, Bolland, Riley, Stallard, Hackworth. Subs: Deeney, Brough, Harrad, Bostock, Rhodes.
Referee: Phil Prosser (W Yorkshire).
