After being pummeled for an hour, the Pompey striker kept his 100% scoring record on the Tractor Boys's turf and then provided David Cotterill with a nice through ball for the Welsh winger to score his first goal for the club.
Ipswich fans will be cursing Nugent and their own strikers as they really should have had the game wrapped up after the first half.
Gareth McAuley's goalbound header was pushed away by Ashdown early on whilst some last ditch blocking from De Laet and Halford prevented Lee Martin from scoring.
An unchanged Pompey side couldn't get a foothold in the game but were presented with a glorious opportunity to take the lead after the ball bounced kindly into Kitson's path but his shot was straight at Marton Fulop when it should have found the back of the net. A confident striker certainly would have buried that chance.
However, it wasn't just Kitson who was guilty of missing sitters as 17-year-old starlet Connor Wickham and his strike partner Jason Scotland also wasted superb chances to give the home side the lead.
Scotland should have turned in Carlos Edwards' cross from five yards but somehow managed to fire wide but an even more astonishing miss was to come from Wickham, who somehow headed wide from point blank range when presented with an open goal.
The half-time stats were clear to see. Ipswich had 15 shots on target, Portsmouth had just one. The 930 odd Pompey fans who had made the journey to Suffolk must have wondered how on earth their team weren't behind.
The Ipswich dominance continued after the break as Wickham again squandered a great chance to score after heading Edwards' cross straight at Ashdown from the kick off.
Scotland then fired a couple of shots wide before Pompey were awarded a free kick in the Ipswich half. Cotterill crossed the ball to Nugent who made himself some space in the box before drilling the ball past Fulop into the corner of the net.
Nugent celebrated wildly to wind up the home crowd who then booed him for the rest of the game but the goal, which had come well against the run of play, stifled Paul Jewell's men and Pompey took control of the game.
Goalscorer soon turned provider as Nugent attacked Town on the break and slotted a nice through ball for the onrushing Cotterill who lobbed the diving Fulop to ensure that Portsmouth would win their fourth game on the trot.
The only question would be if Ashdown would keep a fourth consecutive clean sheet and when a late penalty appeal from Tamas Priskin was waved away, you just knew it was going to be our day as Pompey fans partied in the monsoon that had engulfed Portman Road during the game.
To put it bluntly, this was as "smash 'n' grab" as results come. Pompey were poor in the first half because the players were being outfought and on the rare occasion they had the ball, they cheaply gave it away.
If it wasn't for Ipswich's profligacy then we would have been three or four goals down at the break. Thankfully the second half performance was much improved and the goal was the turning point as it settled the team down and the home side ended up making basic errors.
On this performance, I wouldn't want Steve Cotterill to sign David Norris. He looked lacklustre whilst Joel Ward worked hard and showed that he can do a job in his central midfield role.
This win has seen Portsmouth climb to 13th in the Championship and surely any thoughts of relegation have been banished for good now.
Talk of a play-off push is silly as we'd have to win every game from now until May but a top half finish would be an excellent achievement for this football club after the year of turmoil it has suffered.
Pompey Player Ratings
Jamie Ashdown: 7 - Forced into some good saves.
Ritchie De Laet: 7 - Keeps on improving.
Greg Halford: 6 - Looked a bit shaky at times.
Ricardo Rocha: 6 - Not as influential as usual.
Hermann Hreidarsson: 6 - Got better as the game went on.
Hayden Mullins: 5 - Got caught out too often.
Jonathan Hogg: 6 - Gave his all.
David Cotterill: 7 - Lovely finish for the second goal.
Joel Ward: 6 - Worked hard.
David Nugent: 8 - The difference maker.
Dave Kitson: 5 - Poor once again.
Substitutes
Darryl Flahavan
Aaron Mokoena (Ward 66): 6 - Slotted in nicely.
Carl Dickinson (Nugent 90): N/A - Time eating switch.
Nadir Ciftci
Tom Kilbey
Kanu (Mullins 90): N/A - Time wasting sub.