MATT TAYLOR put his St Mary's handball behind him by scoring his first-ever Premiership goal.
Left-back Taylor, in his 100th appearance for the club, cancelled out Malcolm Christie's 35th minute opener - and erased the memory of Saturday's FA Cup defeat by helping Pompey to their first Premiership win of 2005.
The 23-year-old's initial left foot drive was parried by Mark Schwarzer at the near post, but midfielder Aliou Cisse's neat lay off provided him with his second opportunity, which he drove right-footed into the roof of the net for his first goal since his FA Cup equaliser at Anfield a year ago.
Taylor's 40th-minute leveller was the least Pompey deserved.
Christie, in his first start since breaking his leg 16 months ago, had given Middlesbrough the lead when he bundled home from close range after Konstantinos Chalkias had failed to hold on to Ray Parlour's drive.
But two minutes earlier, Pompey should have had a penalty when Michael Reiziger tripped matchwinner Yakubu, who was back to his best against the team he bagged four against on the final day of last season.
Chalkias again looked suspect at crosses but produced his best save for Pompey when he denied Bolo Zenden from point-blank range in the 51st minute, following Jimmy Floyd Hasselbaink's through ball.
And Yakubu completed the turnaround on the hour, claiming his 12th goal of the season despite suggestions that Frank Queudrue had got the crucial touch.
It was the least Yakubu deserved but it was the brilliance of Ricardo Fuller, who replaced the suspended Diomansy Kamara in the only change from the side that lost at St Mary's, that created the winning goal.
Fuller's mazy run and excellent cross from the left gave the Nigerian the chance to put Pompey's miserable January behind them.
A late tackle from Parlour on Richard Hughes threatened to take the gloss off a first win in six Premiership games, but the former Bournemouth midfielder recovered - and Velimir Zajec handed debuts to substitutes Ioannis Skopelitis and Alexandra Rodic.
The only disappointment was the crowd of 19,620, the second lowest at Fratton Park in the Premiership.
Coach Joe Jordan said: "This was a huge win, it's a big relief and gives everyone confidence. We were very disappointed not to get the penalty before their goal but the reaction from the players after going behind was marvellous."
Middlesbrough boss Steve McLaren hailed the return of Christie, saying: "Having Malcolm Christie back is like signing a new player. He certainly provided us with energy.
"We didn't deserve to lose, we spent the last 15 minutes in their penalty box but we're just not getting the rub of the green."
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