The bright Blues were relatively untroubled by league above Posh and won it thanks to well-taken first-half strikes from Ryan Tunnicliffe and Ronan Curtis.
In what was the first fixture at Fratton Park in front of supporters since last December, there were 4,077 in attendance.
And, despite head coach Danny Cowley having just 12 contracted players available to him, the Blues supporters would have been satisfied with this display a week out from the League One kick-off.
Pompey were looking bright and took the lead on 24 minutes. Posh goalkeeper Christy Pym's poor clearance went straight to Tunnicliffe, who superbly slotted into the empty net from just outside the area.
Former Blues target Sammie Szmodics was then guilty of two misses as the visitors looked for a way back into the game.
First, he somehow headed over from close range after being picked out by a sweet Joe Ward cross on 34 minutes.
Former Pompey full-back Dan Butler laid on for Szmodics three minutes later, but he fired wide from just inside the area.
The Blues then doubled their advantage five minutes before the break as Curtis spectacularly curled into the far right corner from around 20 yards out.
Pompey could and should have had a three-goal advantage at the break, only for a superb Nathan Thompson block.
The ball made its way to John Marquis after Pym gave it away away under pressure from Curtis, but the Blues forward saw his effort blocked by Thompson.
Thompson, being jeered with every touch on his Fratton return was then involved in a heated exhange with Marquis just before the hour.
The pair had hold of each others shirts before falling to the ground and having a brief face-off, with both booked.
Pompey continued to create chances throughout the second half but couldn't find a third but can take comfort from a vibrant display.