Pompey fought from behind to draw away to Championship opposition for the second time in a week.
In front of a healthy crowd at Luton, they soon found themselves trailing to an early finish from tricky striker Elijah Adebayo.
But Gassan Ahadme immediately drew them level – taking the forward’s tally for pre-season to an impressive eight strikes.
Former Hatters midfielder Ryan Tunnicliffe was handed the captain’s armband on his return to Kenilworth Road.
Meanwhile, the hosts included ex-Fratton defenders Sonny Bradley and Dan Potts in their line-up, while Kal Naismith was on the bench.
There was a rousing reception for Luton assistant Mick Harford ahead of the game, with the club legend having recently announced he is battling prostate cancer.
It was his side that were quicker to emerge from the blocks and when Alex Bass missed a ball into the box, a shot from Potts was blocked by the well-placed Sean Raggett.
And they took the lead on 10 minutes, as Adebayo collected Fred Onyedinma’s pass and neatly bent the ball home.
The leveller came almost immediately, however, as AHADME raced clear and slotted past Simon Sluga to continue his impressive friendly form.
There were not too many other clear-cut openings before the interval, although the better of the half-chances fell to Luton.
An angled Onyedinma effort deflected off Kieron Freeman and into the arms of Bass, while Adebayo was also denied.
And when Onyedinma tried to find Harry Cornick in the area, the keeper improvised and used his chest to get the ball to safety.
Meanwhile, Ronan Curtis and Ahadme had attempts blocked in quick succession towards the end of the first half.
Half Time: Luton 1 Pompey 1
Bass was called into action soon after the restart, getting down to his left to keep out Adebayo’s header.
But Pompey threatened when possession was overturned on the edge of the box and the ball worked out to Ahadme.
The on-loan Norwich forward then sent it into the mixer, where the onrushing John Marquis could not quite make contact.
Bass was still the busiest of the two keepers, however, and parried clear Cornick’s effort following a quick break down the right.
Not that it was one-way traffic and a teasing Curtis cross missed two Luton defenders, but also Marquis at the back post.
The usual slew of substitutions slowed down proceedings and ensured the contest limped along for a bit.
But James Bree woke everyone up with a low shot that flashed past Bass’ grasp and inches past the post.
And Potts went even closer to finding a winner for the Hatters when he sent a firm header crashing against the crossbar.
Jayden Reid had replaced Curtis for the final few moments, but picked up a knock, so the Republic of Ireland international had to come back off the bench.
And the closing stages passed by without too much incident to ensure Pompey headed home on the back of a respectable result.
Luton (4-2-3-1): Sluga (Shea 65); Bree (Kioso 80), Burke, Bradley (c) (Naismith 65), Potts; Rea (Osho 65), Campbell (Pereira 80); Cornick (Mpanzu 65), Clark, Onyedinma (Gomes 65); Adebayo
Goals: Adebayo 10
Subs not used: Isted, Hutchinson, Beckwith
Pompey (4-2-3-1): Bass; Freeman (Johnson 73), Raggett, Robertson (Mnoga 81), Brown (Trialist A 81); Tunnicliffe (c) (Trialist C 81), Williams (Trialist B 73); Harness (Hackett-Fairchild 73), Ahadme (Jacobs 81), Curtis (Reid 81 (Curtis 88)); Marquis (Harrison 81)
Goals: Ahadme 12
Sub not used: Bazunu
Referee: Keith Stroud