There was more generosity on display from the Blues to allow Macauley Bonne to break the deadlock at the end of an even first half.
But the Tractor Boys were on top throughout the second period and Conor Chaplin doubled their lead against his former club.
And it quickly got worse for Pompey, with Sone Aluko and Wes Burns both finding the target to leave Fratton Park stunned.
Danny Cowley made one change from the side that were beaten on the road at Rotherham at the weekend.
Ronan Curtis returned from suspension to replace Connor Ogilvie, with Shaun Williams dropping back into defence.
Chaplin was in the visitors’ forward line, while there were also plenty of familiar faces in the dug-out, with Paul Cook’s backroom team including Gary Roberts and John Keeley.
There was not too much between the sides during the first half, but it was arguably Pompey who settled quicker.
And Christian Walton would have been relieved to see the ball fly safe after his clearance hit Curtis in the opening seconds.
Bonne nodded a cross from Lee Evans over the bar at the other end, but clear-cut openings were not exactly flowing.
The best arrived for the hosts on 15 minutes, with Marcus Harness only able to slot narrowly wide after meeting a low delivery from Lee Brown.
It was still the Blues looking the more assured side as the interval approached, but they were unable to properly test Walton.
And they undid all their good work by gifting the Tractor Boys an extremely soft opener on 41 minutes.
Gavin Bazunu took too much time on the ball and was dispossessed Bonne, who still had to keep the ball in play and then slam it into the net from an acute angle.
Ipswich Town 1
The Tractor Boys were quicker out of the blocks once the action restarted and they soon doubled their advantage.
Chaplin became the second striker to haunt his former club in a matter of days, neatly turning home a low Janoi Donacien delivery.
And he then turned provider to feed Aluko, whose shot squirmed under Bazunu’s hand and rolled over the line.
Cowley made his first substitution just past the hour mark, with George Hirst on to replace John Marquis up front.
And a second switch in the forward line followed moments later, as Harness made way for Reeco Hackett.
Pompey were being frustrated in the attempts to get back into the contest and struggled to find any rhythm going forward.
The third – and final – switch was in the heart of defence on 73 minutes, with Ogilvie coming on for Williams.
But it failed to halt the tide and substitute Burns soon turned in a low Donacien centre to increase the Tractor Boys’ lead.
The Fratton faithful made their displeasure known, but there was warm applause for Chaplin when he was brought off.
Walton was finally called into action late on and denied the hosts a consolation by making a smart save from Hirst.
But that was about as good as it got for Pompey, who must now find a way to recover ahead of Saturday’s tricky trip to Accrington.
Pompey (3-4-3): Bazunu; Freeman, Raggett, Williams (Ogilvie 73); Romeo, Tunnicliffe, Morrell, Brown (c); Harness (Hackett 69), Marquis (Hirst 64), Curtis
Booked: Curtis, Harness
Subs not used: Bass, Thompson, Azeez, Jacobs
Ipswich (4-2-3-1): Walton; Donacien, Nsiala, Edmundson, Penney; Evans, Morsy (c); Aluko (Celina 85), Chaplin (Harper 78), Edwards (Burns 64); Bonne
Goals: Bonne 41, Chaplin 54, Aluko 58, Burns 75
Booked: Edmundson, Morsy
Subs not used: Hladky, Burgess, El Mizouni, Barry
Referee: Joshua Smith
Attendance: 16,301 (1,260 away fans)