Battling Pompey were left empty-handed at Birmingham as Nathan Redmond’s 86th-minute volley condemned them to a 1-0 defeat.
The spirited Blues looked set to earn a well-deserved draw from their trip to the Midlands before the pacey wide man’s stunning strike past the helpless Stephen Henderson.
The win sees Birmingham move up to third in the table, while Pompey remain stuck in 17th following their ninth away defeat of the season.
Birmingham started brightly and had Pompey on the back foot when Marlon King peeled off his marker at the back post to set up Adam Rooney.
However, Henderson did well to deny the striker the early breakthrough and dealt comfortably with Keith Fahey’s long-range drive two minutes later.
Pompey replied with a Hayden Mullins shot that failed to test Boaz Myhill, while Marko Futacs could have done better when Kelvin Etuhu set him up in the box after a terrific surging run down the right wing.
When Jonathan Spector robbed Joel Ward of possession on 15 minutes before shooting well wide, it marked a period of possession where the home side threatened the visitors’ goal.
Rooney failed to make the most of a poor Tal Ben Haim backpass, while Fahey again tried his luck from the edge of the box.
However, Pompey continued to battle away and ended the first half unlucky not to be in front.
Etuhu shot wide after a neat lay-off from Liam Lawrence, Myhill had to be alert to deny Ward after he was set up by Etuhu, while Ward was again unlucky after Erik Huseklepp set him up with a chance to give the Blues the lead.
In the second half, Jason Pearce did well under pressure to deny the home side the breakthrough on 49 minutes, before he went up the other end to head Lawrence’s well-flighted free-kick in the arms of Myhill.
Birmingham responded by bringing on Redmond for the ineffective king, and the move worked as he injected pace into the home side’s attack.
He put pressure on Ben Haim when he attempted a backpass to Henderson, but Rooney was denied as the keeper spread himself well.
However there was little Henderson could do as Redmond fired Brum into the lead with a sweet drive on 86 minutes.
Pompey brought on Benjani for Futacs and Kitson for Ethuhu as they attempted to rescue something from the game.
But it failed to spark a sterling comeback from the visitors, with Mutch and Rooney both going close to extending the home side’s advantage in the dying minutes.