It was the first Pompey away victory of the season, condemning Rovers to a ninth Ewood defeat, their home form the scourge of their campaign.
Blackburn boss Graeme Souness has pointed the finger at luck as being a major reason why his side find themselves where they are but today had no complaints having seen Portsmouth put in a classic away performance.
Souness said afterwards: "It was very disappointing, we were not creative enough. We had lots of the ball but did not do enough with it.
"We haven't performed, and not treated our fans to entertainment this year. I can understand the booing, we've let them down."
The visitors were ahead inside 17 minutes, Teddy Sheringham's free-kick finding a critical gap in the Blackburn wall and trickling in off the inside of the post.
Tugay's leveller 20 minutes later owed much to good fortune as his drilled shot ricocheted off two bodies before being woefully turned into his own net by an unlucky Matthew Taylor.
Still, Pompey picked themselves up and top scorer Yakubu scored his second match-winner in a week with nine minutes left, giving the South Coast side a real fillip in their battle against the dreaded drop.
Pompey manager Harry Redknapp was clearly delighted at securing two successive wins for the first time in the Premiership.
"This could not have come at a better time for us, we needed that one," he said.
"But, there is a long way to go so we're not going to get carried away. There is all to play for."
Blackburn had appeared to put themselves out of immediate danger with an impressive victory at Aston Villa last week but, a chronic failure to pick up points in front of their own fans has proved a real headache for Souness.
Both managers chose to stick with their previous starting elevens, and it was Portsmouth was started the better, Taylor making his way to the byline before cutting the ball back only for Craig Short to hammer clear.
Andy Cole was always looking to play free-scoring strike partner Jonathan Stead in, and on 14 minutes his attempted pass was cut out by the impressive Arjan De Zeeuw.
Then, after Stead half-volleyed a decent opportunity well over the top, Portsmouth sent their raucous travelling support into raptures when they opened the scoring.
Nigerian forward Yakubu won a free-kick from Andy Todd and Sheringham curled a cute shot beyond Brad Friedel's despairing left hand and in off the post.
Just four minutes later, Taylor whistled a drive inches beyond Friedel's far post after good work from Yakubu as Portsmouth looked to increase their lead.
Blackburn finally posed a real threat on 23 minutes, Cole slipping Stead behind the backline, but the youngster delayed his shot too long and Shaka Hislop burst off his line to save well.
Suddenly the game became stretched as at the other end, Yakubu held up play, timed an impeccable pass into Steve Stone's path but this time Friedel was on the spot to block superbly.
Sheringham should have done better when Alexei Smertin's incisive run and Stone's perceptive pass picked him out but he dragged a shot well wide.
However, Blackburn got themselves what seemed a crucial equaliser on 37 minutes when Brett Emerton cut a corner back into Tugay's path.
The Turk's sweetly-struck low shot rebounded off a body in the box and as Taylor tried to clear he merely succeeded in putting the ball into his own net.
As the half drew to a close, Yakubu headed Stone's centre over the top and Cole then fired a decent chance straight at Hislop.
After the break Blackburn should have had the initiative but some solid defending from the Portsmouth back four stopped them creating too many clear opportunities.
Emerton briefly threatened, swinging over an excellent cross only for captain Garry Flitcroft to head wide and then freeing up Cole whose shot swung away from goal at the last moment.
Yakubu remained a real threat on the counter-attack. In the 68th minute he wriggled free of Todd and tried to find Sheringham but Friedel was bravely off his line to stop.
Pompey boss Redknapp sent on Lomano Lua Lua to join Yakubu and together they terrorised the Blackburn defence.
Lua Lua displayed his menace two minutes after coming on, cutting inside and lashing a low drive inches past the far post.
Then, as Rovers sought what would have been a vital winner, substitute Dwight Yorke and Cole combined to set up Michael Gray and his low drive was well palmed away by Hislop.
But, the visiting side were to have the last laugh and it all came from the searing pace of Lua Lua.
Receiving the ball on the halfway line he accelerated past three challenges and bore down on goal only for Lucas Neill to scramble across and get a foot in.
However, it broke to Yakubu and he tucked a super finish underneath a sprawling Friedel to send the travelling support into wonderland.
The Blackburn players left the pitch to a chorus of boos and with a despondent atmosphere heavy amongst them. There is a lot of work left yet if they are to stay up.
Man of the match: Arjan De Zeeuw - A colossus at the back for Pompey, his towering display denied Rovers time and time again.