A goal in each half saw Pompey’s young guns deliver victory at Fleetwood.
Jamal Lowe and Oli Hawkins did the damage to give Kenny Jackett’s men their second win of 2018 with a 2-1 success.
With injuries and suspensions biting, Jackett fielded a starting XI with an average age of just 22.5 at Highbury Stadium.
They were looking comfortable until an arcing 25 yarder from sub Conor McAleny flew in with eight minutes left, to set the game up for a nervy finale.
But Pompey held out for the win on the longest away trip of the season - and narrowed the gap to two points on the top six.
It proved a start low on quality with long-range efforts the best either side could conjure.
The best of those came from Bobby Grant, whose 20 yarder wasn’t too far wide after 20 minutes.
But that changed after 24 minutes as Ben Close’s 20-yard shot was blocked and Lowe was on hand to snaffle the follow-up and put his side in front.
Pompey nearly doubled their advantage after the restart, as a scramble ensued from a corner with the ball heading in off a red and white shirt before it was hacked away.
Ashley Hunter’s 25 yarder wasn’t too far past Luke McGee’s left-hand post after 51 minutes.
Hawkins was a whisker away from a second as he produced some close control and fired just over from 20 yards in the 62nd minute.
Close then dragged his shot wide from 20 yards after sub Wes Burns cracked a shot wide from a tight angle on the counter.
May looked to have settled it with 20 minutes left as he hit a peach of a 30 yarder which came back off the inside of the post.
The goal came five minutes laster as Hawkins bundled home the loose ball as Alex Cairns parried Lowe’s angled drive.
But then McAleny buried a classy, dipping finish from 25 yards to set the game up for a grandstand finish.
Pompey held on, however, through four minutes of stoppage time to secure the points.