Ryan Taylor’s second-half penalty earned Pompey their first win of 2014 and three valuable points to move them six points clear of the League Two relegation zone.
Following Gary Doherty’s foul on Wes Fogden, Taylor converted his second goal for the Blues since his Fratton Park arrival earlier this month.
It was the perfect response from the visitors after a first half often spent on the back foot, with Wycombe enjoying the majority of the play.
On three occasions Pompey keeper Trevor Carson had to be at his best to deny Matt McClure, twice, then Reece Styche as the Chairboys’ striker looked certain to score from point-blank range.
All the Blues had to show from their first-half efforts were chances for Jake Jervis and appeals for a penalty when the recalled Andy Barcham was brought down.
However, neither opportunity altered the scoreline as both teams went into the break on level terms.
Pompey broke the deadlock on 48 minutes when Taylor sent keeper Matt Ingram the wrong way from the penalty spot.
That sparked the visitors into life, with Jervis firing over at the near post from a Fogden cross.
But it also roused the home side, with Josh Scowen shooting straight at Carson, Marvin McCoy going close and then the Blues breathing a huge sigh of relief when the ball struck a post and then rolled along the goalline amid a crowded penalty area.
Pompey looked a threat on the counter-attack as Wycombe piled forward in search of an equaliser.
However, it was the home side who came closest to scoring, only for Gary Doherty’s close-range effort to be ruled out for a foul.
That brought huge cheers from an impressive Pompey following behind the goal.
And it was soon followed by further cheers on the final whistle as Pompey picked up only their second away win of the season to climb up to 18th in the league table.