Michael Brown's late winner saw Pompey come from behind to end Watford's unbeaten run away from home and extend their own unbeaten run to four games.
Despite the five goals this game was a scrappy affair highlighted by a couple of excellent strikes from Hayden Mullins and Michael Brown. John Utaka missed out with a sore hamstring so Nadir Ciftci replaced him.
Watford had started brightly as they looked to expose Pompey down the wings; a lesson the home side would not learn all game. But a stunning 25-yard volley from Mullins (of all people) gave Steve Cotterill's men the lead in spectacular fashion. It'll be surprising if there is a better goal scored at Fratton Park all season!
Pompey created a couple more chances as Lawrence skewed his shot wide after Brown played him through on the counter-attack and Nugent also shot just wide from distance.
Watford had offered little in a poor game up until the break, but Malky Mackay must have riled them at half-time as the Hornets came out buzzing in the second half.
The Portsmouth defence were swarmed with a number of corners early in the second half and an equaliser looked certain, only for Jamie Ashdown to pull off a tremendous triple save from close range to preserve Pompey's lead.
However, Ashdown couldn't keep out Martin Taylor's header from Jordan Mutch's corner as nobody was marking the Watford centre back despite the fact that he was clearly the biggest player on the pitch.
And Pompey fell behind soon after as Stephen McGinn turned in Michael Bryan's cross from the right as the hosts failed to contain Watford when they were coming forward down the wings.
Thankfully, falling behind galvanised Pompey instead of demoralising them like it would have a month ago and Dave Kitson bagged an equaliser a couple of minutes from the restart.
The ball broke kindly to him as the referee might have awarded a free kick but the former Reading striker made no mistake of taking advantage of the situation and drilling the ball past Scott Loach into the corner of the net.
The comeback was complete on 80 minutes as Brown curled in a sublime third goal that would ultimately seal Pompey's third home victory in a row.
The visitors piled the pressure late on and Troy Deeney could only put the ball wide from two yards out and so the five minutes of stoppage time were navigated safely, meaning the majority of the 16,606 crowd left Fratton Park happy.
This is a very good result for us for a few reasons.
Firstly, the way we came back again, like at Middlesbrough, illustrates the character that this team has. Character alone is something that will get you far in the Championship and add that to a good first XI and I think we will do well in this league.
Secondly, we have beaten a good team in Watford. Our previous wins were against poor opposition in Leicester and Bristol City but Malky Mackay brought a confident, high-flying team down to Fratton Park and we've managed to beat them despite not playing at our best.
And finally, this result has seen Portsmouth climb to 17th in the table, 3 points clear of the relegation zone and only 6 from the play-offs. Talk of a promotion push may be a little premature but we're certainly going in the right direction.
Pompey Player Ratings
Jamie Ashdown: 7 - Fantastic triple save but not tested too much otherwise.
Joel Ward: 6 - Still a bit suspect, Cotterill is looking at bringing in Greg Halford to replace him.
Aaron Mokoena: 6 - Made a couple of mistakes but also a couple of crucial blocks.
Ricardo Rocha: 6 - Not his best performance.
Carl Dickinson: 6 - Watford wingers occasionally got the better of him.
Liam Lawrence: 6 - Average performance.
Michael Brown: 8 - Good goal capped workmanlike performance.
Hayden Mullins: 8 - Superb strike for the first goal.
Nadir Ciftci: 6 - Didn't look out of place but faded.
David Nugent: 6 - Worked hard as always.
Dave Kitson: 7 - Took his goal well.
Substitutes
Darryl Flahavan
Ibrahima Sonko (Ward 90): N/A - Brought on to win stoppage time headers.
Richard Hughes (Ciftci 77): N/A - Didn't really notice him.
Kanu (Nugent 74): N/A - Added extra strength to the side.