Kyle Vassell scored the only goal of the game as Peterborough saw off Leagoe One newcomers Rochdale to make a winning start to the campaign.
Vassell's close-range finish in the second half proved decisive in an evenly contested game at Spotland.
Nathaniel Mendez-Laing saw a 20-yard curling shot pushed over by Josh Lillis in the 11th minute. The Posh wideman beat the Dale goalkeeper from similar distance soon afterwards but was frustrated again as the ball struck the underside of the crossbar.
The home side finished the first half strongly, Rhys Bennett controlled Joe Rafferty's pass and forced a great save from Ben Alwick with a smart turn and shot towards the top corner of the net. Alwick parried Ian Henderson's long-range drive and then smothered George Donnelly's volley.
Former Manchester United boss Sir Alex Ferguson was among the crowd to witness Darren Ferguson's men take the lead in the 61st minute when Conor Washington teed-up Vassell for a simple finish from six yards out.
Donnelly had Rochdale's best chance of the second period when he raced through on goal only to pull a shot desperately wide of the target.