Exeter City four match unbeaten run came to an end at Fratton Park.
Second half goals from Marlon Pack and Joe Morell were enough to earn the home side the three points.
Following the draw at home to Forest Green Rovers in the previous game, manager Gary Caldwell made three changes to the team. Joe White was given his full debut, with Jevani Brown and Kegs Chauke coming back into the starting XI for Archie Collins, Jack Sparkes and Jay Stansfield.
An almost perfect start to the game for City inside the first five minutes, Sam Nombe forced an unbelievable save out of Matt Macey in the Pompey net, sending the ball behind for a corner.
Only a few moments later and Portsmouth almost opened the scoring for themselves with both Owen Dale and Colby Bishop having an effort on goal, but to no avail as the ball eventually flew over the bar for a goal kick to City.
With 14 minutes played, the home side came close once again, Dale and Bishop both causing issues in the City defensive third, with the header on goal flashing just wide of Blackmans far post.
With the game just going past the halfway stage of the first half, Nombe was causing a problem for the Pompey defence every time he got the ball, but all that was lacking was the finish at the end.
Just passing the 30th minute mark, City were very much the team on top, going close once again this time was the combination of new boy White and josh Key down the left-hand side, but the ball was cleared away for a corner.
A fantastic attack from City in the 36th minute led by Brown, White and Nombe led to City almost taking the lead once again. The ball eventually fell to Key waiting at the edge of the area but the left-wing backs curling effort was excellently saved by Macey and tipped over the bar.
With half time saw the first sub of the game for City, with Collins coming on to replace Chauke for a straight swap in the middle of the park.
A first effort on goal in the second half for Pompey had the home side almost taking the lead. A well driven effort from Connor Ogilvie had Blackman scrambling across his area to tip it round the post.
Then straight up the other end came City, with Brown leading a four on two charge, but the tricky forward made to much of a heavy touch on the ball and Macey smothered him, another big chance for City.
With just over ten minutes of the second half played, Pompey were able to take the lead courtesy of a stunner from their captain Marlon Pack, leaving Blackman no chance with a strike from distance. Giving their fans a chance to make themselves heard inside a very packed Fratton Park.
Not long after Pompey taking the lead, City were on the attack in another four on two scenario but were again unable to make it count. In the midst of the attack there was a huge shout from the City fans for a penalty after White went down in the box, but the ref was having none of it and waved it away.
With City needing to get back into the game, Gary made another change, this time a much more attacking one with Stansfield making his way onto the pitch in place of Harry Kite. This was very quickly followed by the first booking of the game for Alex Hartridge for a late challenge.
Portsmouth made it 2-0 with 15 minutes left to be played, with Joe Morrell picking up a loose ball in the City penalty area and striking the ball straight at Blackman, but the big man between the sticks spilled the ball into his own net.
Pompey could have made it 3-0 in the last ten minutes, but an inch perfect challenge from Hartridge stopped Bishop getting a shot on goal.
With the game into the dying moments of the five added minutes, it gave Hartridge a chance to have a sighter on goal from 35 yards but the centre backs effort on goal sailed over the bar.
The next game for City is back at home against promotion chasing Barnsley on Tuesday January 24th for a first clash between the sides at SJP since 1980. Click here for tickets.
Portsmouth: Macey, Swanson, Raggett, Towler, Ogilvie, Tunnicliffe (Thompson), Pack ©, Morrell, Dale, Bishop, Jacobs (Curtis)
Subs not used: Oluwayemi, Hume, Hackett, Pigott, Scarlett
City: Blackman, Key, Sweeney ©, Diabate, Hartridge, Caprice, Kite (Stansfield), Chauke (Collins), White, Brown, Nombe
Subs not used: Lee, Stubbs, Grounds, Sparkes, Harper,
Referee: Ollie Yates
Attendance: 18719 (1589 Away)