Inconsistent Pompey grabbed a notable scalp as they impressively returned to winning ways.
Plymouth Argyle arrived at Fratton Park seeking to make it a double over their hosts for the season and cement their position within the League Two play-offs.
But instead they stumbled across the Blues on one of their good days, particularly during a swashbuckling second half.
There were a number of boos from home fans when the first-half whistle sounded, reflecting a lacklustre and unimaginative opening 45 minutes.
During that period, Andy Awford’s men managed one shot on target.
But it was a very different story in the second period as Pompey turned on the style.
A Jed Wallace special within a minute of the restart, this time left-footed from outside the box, set the hosts on their way to a second win in nine games.
The lead was increased when Ryan Taylor headed home Dan Butler’s excellent left-wing cross from a seemingly impossible angle on 76 minutes.
Substitute Olly Lee’s thumping volley two minutes later sparked some late nerves.
But a defence magnificently marshalled by Blues loanee Nyron Nosworthy and Joe Devera stood firm.
Plymouth’s desperate bid for a late equaliser was not helped by the dimissal of Curtis Nelson late on.
He received a second yellow card and the visitors had to play out the closing stages with 10 men.
Throughout the contest, the dangerous Reuben Reid was not allowed a sniff.
And once again Wes Fogden’s energy was outstanding for Pompey.
The 2-1 victory may not have lifted the Blues up the table – they remain in 14th spot – but it meant so much to the supporters who feared their season was petering out to nothing.
There was one change to the side who were denied victory at Carlisle so cruelly, with the experienced Nosworthy coming into the side.
He replaced Ben Chorley, whose back problem forced him off at half-time during the Brunton Park draw.
Nosworthy was able to declare himself available despite being substituted in the same match, following a gashed head which required stitches.
The veteran received the nod at centre half ahead of Adam Webster, another player who came off the bench in the 2-2 draw on Friday.
Elsewhere, Nicky Shorey was a surprise inclusion in the squad after not featuring since the home defeat by Southend in January.
He replaced Nosworthy on the bench, with still no room for Johnny Ertl and loanee Cole Kpekawa in the match-day 18.
Soon after kick-off, encouragingly Pompey tested Luke McCormick within the opening minute through Matt Tubbs.
It was a wonderful pass from Fogden inside Tareiq Dennis-Holmes to send the striker through down the right and his angled shot was deflected by the keeper’s legs for a corner.
Plymouth’s response was instigated on seven minutes by sloppy play between Dan Butler and Nigel Atangana, presenting the ball to Zak Ansah.
The youngster burst down the middle with the defence opening up in front of him, before driving in a left-foot shot which Paul Jones did well to push out.
In the 12th minute, Jones hammered the ball down the pitch and when Peter Hartley’s attempted headed clearance looped up into the air, it fell to Ryan Taylor who fed Jed Wallace.
However, from an immensely promising attack, Wallace could only deliver his cross from the left into the Milton end.
It was a lively opening and when Reuben Reid squared the ball to Dominic Blizzard, the midfielder rifled a right-foot shot towards goal which brought a low stop out of Jones.
On 20 minutes, Tubbs pounced on a mistake from a Plymouth defender to gain the ball but his right-foot shot from just inside the box screwed well wide.
A patient build-up from the Blues on 25 minutes presented the ball to Atangana, who took one touch before firing a 25-yard effort which drifted comfortably wide.
The game soon became flat, yet it took a crunching tackle from Nosworthy on Jason Banton on 38 minutes to lift matters and spark Pompey forward.
In the subsequent move, Fogden chased a lost cause to keep it in at the touchline ahead of Carl McHugh, with Tubbs picking up the loose ball and firing a shot wide of the target.
The visitors should have taken the lead on 43 minutes.
Dunne’s mistake gifted the ball to Ansah who slipped the ball inside to Banton and the midfielder’s woeful left-footed shot didn’t even test Jones.
It was goalless at half-time but within 53 seconds of the restart the hosts had the lead.
Wallace accepted a pass from Tubbs down the right and cut inside before firing a 20-yard left-foot shot into the far corner past McCormick.
A moment of magic from the usual source and suddenly Awford’s men found themselves in the driving seat so early in the second half.
On 58 minutes, Banton attempted to thread a pass through to Ansah inside the penalty area but Jones rushed off his line to gather and snuff out the threat.
That was Banton’s final contribution, becoming the first Argyle player to be substituted minutes later with striker Lewis Alessandra replacing him.
That was followed by central defender McHugh coming off for Lee in the 64th minute as the visitors switched to a flat-back four.
Tigerish play from Dunne helped set up another Pompey attack which resulted in Taylor swinging in a cross from the right that was agonisingly out of reach of Wallace charging in at the far post.
At the other end, Nelson missed with a free-header from six yards on 71 minutes as he attempted to convert Alessandra’s right-wing corner, the ball ending up flashing across goal and wide.
Pompey extended their advantage on 76 minutes.
Butler swung in a deep cross from the left and Taylor outmuscled Holmes-Dennis at the far post to head home.
Within two minutes and Argyle had pulled one back, though.
A cross from the left was headed clear only so far as Lee, who crashed a superb right-foot volley into the net from the edge of the area.
The game was proving fascinating and when Wallace curled in a cross from the left, it agonisingly missed his team-mates when all it needed was a touch to finish.
A stunning point-blank stop from Jones then denied Lee from volleying home an equaliser in the 85th minute as the hosts came under some late pressure.
Nelson received a second yellow card and his marching orders following a clumsy challenge on Wallace on the half-way line.
And Awford’s men comfortably held out during five minutes of stoppage time to claim the victory.