Peterborough defensive bad boy Sagi Burton collected his first booking of the new campaign in little more than 90 seconds but then pushed up to sink Tranmere Rovers with a 69th minute header.
Burton came under fire from boss Barry Fry after an atrocious record last season including two dismissals, yet this time he managed to settle and form an effective central pairing with experienced ex-Barnsley man Craig Ireland.
Burton set off as Posh pushed up for one of Andy Legg's trademark long throws and out jumped everyone to steer the ball home as otherwise commanding Rovers goalkeeper John Achterberg came for the ball and missed it.
Legg also outwitted Rovers in the first half, a towering heave reaching David Farrell who slammed a drive against the crossbar, but otherwise Posh failed to beat veteran Achterberg.
The tall Dutchman punched away Adam Newton's cross and then got down to his left to save well when home skipper Curtis Woodhouse was released by Clive Platt.
Achterberg also denied Calum Willock either side of half time, with his work providing the platform for a good Tranmere attacking spell including midfield promptings from former Republic of Ireland international Jason McAteer.
The 33-year-old signed from Sunderland hardly put a foot wrong, keeping it simple with a constant stream of passes. Rovers didn't make much more impact in the first half, with the best effort from new boy Mark Rankine, signed from Sheffield United, also stopped by the alert Mark Tyler.
Posh had a great opportunity to do double their advantage near the end with substitute Leon Constantine, making his first appearance after a move from Southend, setting up Andy Clarke only for the veteran striker to blaze high and wide.