Calum Willock's goal ensured that gutsy Peterborough retained their League One status for at least another week.
It was a deserved win, although Posh were fortunate when Blackpool's Keith Southern blasted his penalty straight at Peterborough keeper Mark Tyler.
Willock netted shortly before the interval as he latched on to a deflected Richard Logan shot.
Peterborough tightened their grip on the match after the break, with Steve Thomson and Logan hitting the bar.
Blackpool: Jones, McGregor, Clarke, Robert Edwards, Coid, Bullock, Donnelly (Anderson 71), Southern, Burns (Shaw 53), Murphy, Parker.Subs Not Used: Edge, Grayson, Doughty.
Peterborough: Tyler, Kanu, St. Ledger, Legg, Arber, Farrell, Huke, Thomson, Boucaud, Logan, Willock.
Subs Not Used: Fry, Coulson, Plummer, Clarke, Purser.
Goals: Willock 42.
Ref: M Jones (Cheshire).