The Irishman put pen to paper on his short-term deal this Thursday ahead of the 5:00pm emergency loan deadline and is now expected to be in contention to make his debut for The Posh on Saturday against Coventry City.
Sheehan has featured twenty-eight times for Phil Parkinson's this season men since joining City from Notts County last summer. His most recent appearance in claret and amber came during the club's FA Cup quarter-final replay at Reading.
Following his arrival at the the ABAX Stadium, Sheehan becomes the second City player to join Peterborough on loan after Aaron Mclean's move to the Cambridgeshire-based side earlier this season.