Posh are now unbeaten in five matches - a well-timed purple patch as a number of their fellow strugglers also continue to pick up vital points.
They lie one point from safety and just four points behind Blackpool, who could not build on their first win under Paul Ince at Watford last weekend.
Pool dominated a first half overshadowed by a serious head injury sustained by their veteran midfielder Barry Ferguson, but Ferdinand put United ahead with a simple finish in the 45th minute.
Blackpool winger Matt Phillips drew a sharp early save from Posh goalkeeper Bobby Olejnik, firing a hard shot into the ground from an acute angle.
It was a bright start from the hosts and Tom Ince was just short of finding a decisive touch when Alex Baptiste flashed across goal in the ninth minute.
Pool top scorer Ince then dragged wide under pressure from United centre-back Michael Bostwick having been played in by a beautifully weighted Phillips pass.
Lee Tomlin had Peterborough's first attempt but Seasiders defender Gary MacKenzie bravely got his face in the way of a powerfully struck effort.
Olejnik produced two more splendid stops as Ludovic Sylvestre and Phillips went for the spectacular before Peterborough took the lead against the run of play.
Jack Payne chipped towards Tommy Rowe in the area, whose header back across goal was nodded home by Ferdinand.
Blackpool could not respond during nine minutes of first-half stoppage time and Peterborough assumed the ascendancy following a quiet start to the second period.
In the 67th minute, Tomlin eased past a tired challenge from Isaiah Osbourne to shoot but Matt Gilks saved well with his legs.
Pool belatedly piled on the pressure and, with nine minutes to play, Phillips picked up a loose ball only to see his goal-bound effort strike Nathan Delfouneso.