Ryan Taylor scored from the spot as Pompey beat Wycombe to record their first victory since Boxing Day.
Both sides had chances in the first half, with Trevor Carson making a couple of fine saves to deny the hosts.
But it was the Blues who got the only goal as Taylor converted a penalty after Wes Fogden had been fouled.
Richie Barker made two changes from the side that drew at Morecambe on Saturday.
Ben Chorley was named captain on his debut, while there was also a start for Andy Barcham, with Sonny Bradley and Jed Wallace dropping to the bench.
Pompey had an early opportunity when Barcham won a free-kick on the edge of the box, but Nicky Shorey’s low cross was cut out.
But it was the hosts who went close to breaking the deadlock on seven minutes, as Matt McClure’s drive skidded across the greasy surface and was just about turned onto the post by Carson.
It was proving to be an open contest and Barcham was next to threaten, embarking on a mazy run that saw him beat several players before seeing his shot blocked.
But the action soon switched to the other end of the pitch, where a corner was headed goalwards and had to be pushed to safety by Carson.
Jake Jervis then tried to race onto Barcham’s incisive pass, but could not keep his balance as he bore down on goal, allowing Marvin McCoy to get the ball clear.
It was end-to-end stuff and Carson did brilliantly to get down to his left and palm away McClure’s arrowed effort on 31 minutes.
And the keeper made an even better save seconds later to keep out a fierce Reece Styche strike that looked destined for the net.
Half Time: Wycombe 0 Pompey 0
Wycombe had the better of the closing moments of the first half, but it was Pompey who finally broke the deadlock five minutes after the restart.
Fogden was brought down by Gary Doherty in the box, referee Charles Breakspear pointed to the spot and TAYLOR stepped up to coolly send Matt Ingram the wrong way.
The hosts immediately set about trying to find an equaliser and Josh Scowen’s low drive was saved by Carson, while the Blues also survived a scramble in the area.
But Pompey were not prepared to simply sit back and soak up pressure, with Barcham drilling a shot inches past the post on 61 minutes.
The visitors survived an almighty scare moments later, though, as a melee in the box ended up with the ball striking the post and rolling along the goal line before being hacked clear.
There were plenty of crosses being swung into the area, but the Blues were displaying resolute defending to repel everything the Chairboys could throw at them.
Barker made his first change on 79 minutes, as Fogden – who had run himself into the ground – made way for Ricky Holmes.
Patrick Agyemang then came on for Jervis as Pompey’s noisy travelling contingent started dreaming of just a second away league victory of the season.
It looked like Wycombe had snatched a point in stoppage-time, but Breakspear ruled the goal out for a foul on Carson and the Blues were able to celebrate a much-needed win.
Wycombe (4-4-2): Ingram; McCoy, Doherty, Johnson, Mustoe; Arnold (Bloomfield 66), Lewis (c), Scowen, Wood (Jeffrey 66); Styche, McClure
Booked: Scowen, McClure
Subs not used: Horlock, Stewart, Hause, Kretzschmar, Kuffour
Pompey (4-4-2): Carson; Alfei, Devera, Chorley (c), Painter; Fogden (Holmes 79), Padovani, Shorey, Barcham (Ertl 90+1); Taylor, Jervis (Agyemang 87)
Goals: Taylor 50 (pen)
Booked: Painter, Ertl
Subs not used: Smith, Bradley, Racon, Wallace
Referee: Charles Breakspear
Attendance: 3,733 (1,112 Pompey fans)