Paul Hayes’ opener was not in the script, but Christian Burgess’ leveller lifted everyone and Gary Roberts then converted a penalty.
An equaliser from Hayes dampened the mood, but a superb Conor Chaplin strike restored the Blues’ lead before the break and Carl Baker made sure of the points after it.
Paul Cook unsurprisingly stuck with the same side that beat Crawley so convincingly the previous week.
It was the hosts who threatened first at a damp and gloomy Fratton Park, with showers frequently interrupting proceedings.
Gary Roberts slipped a quick free-kick through to Milan Lalkovic, but his cut-back was well claimed by Jamal Blackman with Curtis Main waiting to pounce.
The Wycombe keeper was pretty conspicuous with his bleached blonde hair and decked out in a garish pink and luminous green kit.
But it was his opposite number who was next called into action and David Forde denied Aaron Pierre after a Sam Wood cross had caused chaos in the Blues box.
And the visitors were ahead on 10 minutes, with Hayes left in too much space to convert Garry Thompson’s volleyed delivery.
That appeared to spark Pompey into life, although they were growing frustrated at the Chairboys’ attempts to slow things down.
There were cries from the crowd and bench that the visitors were spending too long over set-pieces and referee Tim Robinson was forced to calm an irate Cook down.
And the Blues soon started doing their talking on the pitch, with Main’s header deflected over by Pierre after Baker had picked the striker out.
Unfortunately, Main injured himself during the challenge and was forced to disappear down the tunnel to be patched up.
But he failed to reappear, and Chaplin was brought on to replace him – but not before Wood had almost doubled Wanderers’ lead with an effort that bounced off the crossbar and into the arms of a grateful Forde.
The Blues were starting to take control of proceedings and the newcomer saw his curling effort blocked.
Lalkovic was then unable to dig the ball out from under his feet following a good Enda Stevens’ ball into the box.
But the hosts were level on 34 minutes as Baker picked up a Lalkovic corner and although his shot was saved by Blackman, BURGESS was on hand to bundle the ball over the line.
Chaplin and Baker then both saw strikes blocked as Pompey tried to turn up the pressure and forge ahead.
And that is exactly what they did late in the half after Gareth Evans met Baker’s cross and saw his header blocked by the arm of Sido Jombati.
Robinson pointed straight to the spot and ROBERTS stepped up to emphatically continue his prolific streak with a rocket into the roof of the net.
But, amazingly, there was still time for both sides to add a further goal each in a breathless end to the first half.
First, there was no Blues defender picking up Hayes, who was able to volley a fine curling finish past Forde.
It looked like the sides would go in level at the break, only for a moment of genius from CHAPLIN to lift the Fratton faithful.
The striker ran onto Roberts’ pass, lifted the ball over Anthony Stewart and then, with Blackman off his line, calmly sent a header looping over the keeper and into the net.
Wycombe Wanderers 2
Lalkovic did not return following the interval, with Kal Naismith instead taking up the attacking role wide on the left.
Wycombe had a chance to level soon after the restart, but Stewart was unable to guide Wood’s cross on target.
There was immediately an even better chance at the other end, with Roberts somehow failing to turn home Chaplin’s cross from just a few yards out.
But the Blues did increase their advantage on 53 minutes, as Stevens sent the ball to the far post, where BAKER was waiting to squeeze in a volley at Blackman’s near post.
That did not stop Pompey from trying to add to the lead, however, and Naismith bent a shot narrowly over
Blackman then made a mess of dealing with a couple of routine Chaplin efforts, only to escape any punishment.
Wycombe threw on a couple of strikers in Dayle Southwell and Adebayo Akinfenwa to try to find a way back into the game.
It was still Pompey looking more likely to add to the scoring, though, and Stevens was not quite able to beat Blackman from an acute angle following a flowing passing move.
Ultimately, there were to be no more goals, but that mattered not as the Blues saw the rest of the game out to move up to second in the table.
Pompey (4-2-3-1): Forde; Evans, T.Davies, Burgess, Stevens; Rose, Doyle (c); Baker, Roberts (Hunt 88), Lalkovic (Naismith 46); Main (Chaplin 25)
Goals: Burgess 34, Roberts 43 (pen), Chaplin 45+3, Baker 53
Booked: Roberts, Baker, T.Davies
Subs not used: O’Brien, Clarke, Linganzi, Smith
Wycombe (4-1-4-1): Blackman; Jombati (Akinfenwa 80), Stewart, Pierre, Harriman; Rowe (McGinn 86); Thompson, Bloomfield, Gape, Wood; Hayes (c) (Southwell 80)
Goals: Hayes 10, 45
Booked: Pierre, Jombati, Thompson, Gape, Rowe, Blackman, Stewart
Subs not used: Richardson, De Havilland, Kashket, Freeman
Referee: Tim Robinson
Attendance: 16,262 (489 away fans)