Pompey missed the chance to climb above promotion rivals Hull in the table after suffering a 4-0 defeat at Fratton Park.
Jack Whatmough twice put the ball in his own net, although there was little he could do to prevent the first one.
Sandwiched between was a goal for George Honeyman, while substitute Josh Magennis also found the target in stoppage-time as the Tigers strengthened their position at the League One summit.
Kenny Jackett made one change from the side that eased to victory over AFC Wimbledon earlier in the week.
Michael Jacobs dropped to the bench to make way for Republic of Ireland international Ronan Curtis, who started wide on the left.
Charlie Daniels – who completed his Pompey switch less an hour before kick-off – was watching from the stands, alongside fellow new arrival George Byers.
Chances were at a premium throughout the opening 45 minutes, with both sides having promising spells that usually faded once they reached the final third.
John Marquis did have the ball in the net after collecting a Curtis pass, but referee Ben Toner had already blown his whistle for a foul on Jacob Greaves.
But Hull broke the deadlock midway through the first half and after benefitting from two own-goals at the KCOM Stadium before Christmas, it seemed only fair that Pompey returned the favour.
A free-kick from Honeyman was whipped into the box, where it was met by the head of Keane Lewis-Potter.
Craig MacGillivray got down to his right to make the save, but the ball bounced against the foot of Whatmough and ricocheted into the net.
The hosts might have hit back when Marquis was the recipient of another Curtis pass, with his effort deflected behind.
Whatmough then had to stretch to meet the resulting corner at the back post and could not guide his header on target.
But there were only half-chances before Toner signalled the interval, as Hull were able to keep the Blues at bay.
Half Time: Pompey 0 Hull 1
Jackett made a double change at the break, with Ryan Williams and Andy Cannon replaced by Ben Close and Harvey White.
But it was the Tigers who were quickest out of the blocks and Lewis-Potter had three chances to extend their lead in quick succession.
The first was a stabbed effort from a corner that lacked enough power to trouble MacGillivray, while the second flew wide.
It was the third that was the best of the bunch, though, as a free-kick from the edge of the box flashed narrowly off target.
Pompey had looked organised – if a little lacking creatively before the break, but some sloppy play allowed Hull to double their advantage just past the hour mark.
Mallik Wilks was all alone in the centre to meet Lewis-Potter’s cut-back, although Whatmough was able to dispossess the winger.
His second attempt was then blocked on the line by Sean Raggett, but Honeyman nipped in to slot home.
And they soon had another goal, as the unfortunate Whatmough again turned the ball into his own net, this time while trying to deal with Lewie Coyle’s low delivery.
Ellis Harrison immediately replaced Curtis and soon drew a smart stop from the otherwise underworked George Long.
Pompey were trying to at least salvage some pride and a White free-kick fizzed narrowly over the bar after Richie Smallwood had been booked for fouling Close.
They poured forward in the closing stages, but Hull had plenty of men back and were even able to add some icing to the cake in stoppage-time.
A spell of neat passing play ended with Magennis driving home a precise low effort from outside the box.
Pompey (4-4-1-1): MacGillivray; Johnson, Whatmough, Raggett, Brown; Harness, Naylor (c), Cannon (White 46), Curtis (Harrison 64); Williams (Close 46); Marquis
Subs not used: Turnbull, Bolton, Nicolaisen, Jacobs
Hull (4-2-3-1): Long; Coyle, Jones, Greaves, Elder; Smallwood (c), Docherty (Slater 85); Whyte (Crowley 72), Honeyman, Wilks (Magennis 72); Lewis-Potter (Chadwick 85)
Goals: Whatmough 23 (og), 63 (og), Honeyman 61, Magennis 90+1
Booked: Lewis-Potter, Smallwood
Subs not used: Ingram, Emmanuel, Burke
Referee: Ben Toner