Conor Chaplin registered a priceless last-gasp goal as Pompey performed a smash and grab at Middlesbrough.
The Blues manfully defended their penalty area for much of the game, particularly in the second half, to keep the promotion-hunting Boro at bay.
Then, in seven minutes of stoppage time, Marlon Pack’s corner was picked up by Adrian Segecic and his shot deflected off Chaplin into the net for a 1-0 victory.
John Mousinho’s men had set to drop into the relegation zone, instead a late, late win keeps them in 21st spot.
Here are Pompey’s player ratings…
9. Gustavo Caballero - 7
(Replaced by Adrian Segecic on 63 mins) - Always a threat on the break with his energy and pace as he picked up where he left off against Oxford, while his commitment cannot be faulted. Surprisingly brought off. | Graham Hunt/ProSportsImages
10. Conor Chaplin - 8 - MOM
He's one of our own. Buzzed around and cleverly used the ball in the first half in attacking situations, keeping it superbly. The game became more attritional after the break - then he weighed in with an iconic moment. | Jez Tighe
11. Keshi Anderson - 7
(Replaced by Milli Alli on 75 mins) Frustratingly couldn’t manage to repeat the highs of Oxford, yet always wants the ball, always wants to create and uses the ball cleverly for the majority of time. Need to keep him fit. | Graham Hunt/ProSportsImages
12. Colby Bishop - 7
Some lovely first-time touches in the first half, particularly, found his team-mates, while a backheel from Devlin’s 69th-minute cross represented the team’s first shot. Wasn't a game for attacking and help his team-mates dig in. | Jez Tighe