Two shocking defensive errors by Posh inside three second-half minutes helped donate three points to Hartlepool.
Recalled midfielder Micah Hyde's misplaced clearance enabled Andy Monkhouse to open ths ecoring from close range on 58 minutes.
And on the hour hesitation between Craig Morgan and Joe Lewis presented substitute Richard Barker with a second goal.
George Boyd pulled a goal back for Posh 12 minutes from time with a sweet left-footed strike, but the visitors held on.
Craig Mackail-Smith missed two great opportunties for Posh during a first-half which they dominated.
Posh
Joe Lewis, Russell Martin, Jamie Day, Craig Morgan, Shane Blackett, Sergio Torres, Micah Hyde, Dean Keates, George Boyd, Aaron Mclean, Craig Mackail-Smith.
Subs: Mark Tyler, Scott Rendell, Dominic Green, Charlie Lee, Chris Whelpdale.
Hartlepool
Arran Lee-Barrett, Jamie McCunnie, Ritchie Humphreys, Michael Nelson, Sam Collins, Gary Liddle, Ritchie Jones, Anthony Sweeney, Andy Monkhouse, Joel Porter, James Brown.
Subs: Richard Barker, Alan Power, David Foley, Matty Robson, Jonny Rowell.
Referee: Andy Hall (Birmingham).
Team news and updates will appear here.
Full match report, reaction and photos in Monday's Evening Telegraph.
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Alan.Swann @peterboroughtody.co.uk.
The full article contains 209 words and appears in Peterborough ET newspaper.