Bradley Lethbridge fired a double to extend Pompey Academy’s unbeaten start to 2019 to four matches.
The young Blues delivered a 3-2 win at Plymouth Argyle in the Youth Alliance south west division.
Yet Mark Kelly’s troops made hard work of things, having nearly threw away a three-goal advantage.
Pompey took the lead in the first half when James Whiting fired a shot from the edge of the box into the bottom corner.
And the Blues’ advantage was doubled when Lethbridge collected a pass from Freddie Read before bending an effort home.
The visitors looked to have wrapped up all three points after the interval when Leon Maloney’s cross picked out Lethbridge to convert.
But Pompey allowed Argyle back into the clash, with Rio Garside and Adam Randell reducing the deficit.
And to make matters worse for the Blues, Joe Hancott was dismissed for a second yellow card.
However, Kelly’s side held on, with Klaidi Lolos being sent off for the hosts.
Pompey sit sixth in the Youth Alliance south west division on 29 points – but have a game in hand on fifth-placed Swindon.
The Blues travel to Cheltenham Town, who sit seventh, on Saturday.