Pompey held off a late MK Dons fightback to book their place in the third round of the Emirates FA Cup.
They had earlier fallen behind to a Darragh Burns strike at Fratton Park, only for Reeco Hackett to immediately draw the hosts level.
Colby Bishop then netted penalties either side of the interval to leave the Blues cruising, but Mo Eisa’s reply ensured a nervy finale.
Danny Cowley made four changes from the side that drew with Derby in the league eight days earlier.
Michael Morrison joined a three-man back-line, with Denver Hume wide on the left and Ronan Curtis and Hackett taking up attacking roles.
Connor Ogilvie and Josh Koroma both dropped to the bench, while Owen Dale and Dane Scarlett were not given permission to feature by their parent clubs.
The academy quartet of Brian Quarm, Josh Dockerill, Adam Payce and Koby Mottoh were all named among the substitutes.
Pompey were on top from the start of the contest and skipper Clark Robertson nodded over from an early Hume delivery.
A low angled effort from the lively Curtis was then parried away by Jamie Cumming, with Zak Swanson’s follow-up deflected behind.
The chances kept coming and when Marlon Pack met another Hume cross, his header deflected off team-mate Hackett and landed on the roof of the net.
Curtis was then teed-up by a Jay Mingi cut-back, but could not make a clean connection and fired straight at Jack Tucker.
But MK Dons then took the lead against the run of the play, as Burns collected an incisive Dawson Devoy pass and neatly slotted home.
Not that the Blues were behind for long and they equalised with a similar goal inside three minutes of the restart.
It was a fine threaded pass from Mingi that sent HACKETT racing clear and he bent the ball into the net from the edge of the box.
The game quietened down after that, but burst back into life when Mingi got into the box and drew a clumsy challenge from Josh McEachran.
Referee Sunny Gill immediately pointed to the spot and BISHOP made no mistake, calmly sending Cumming the wrong way.
Mingi might have got on the scoresheet himself on 39 minutes, only to see his effort beaten away by Cumming.
The visitors burst straight down the other end and Nathan Holland raced clear, but Josh Griffiths came to the rescue with a smart stop.
Half Time: Pompey 2 MK Dons 1
Pompey were given a boost shortly after the restart when Bishop went down under pressure from Bradley Johnson and Gill again pointed to the spot.
This time BISHOP slammed his penalty straight down the middle to give the Blues a commanding lead.
There was a chance for the visitors to get back into the contest when the ball could only be scrambled to the edge of the box, but Daniel Harvie ballooned his shot high over the bar.
Cowley freshened things up with a change just before the hour mark, as Ogilvie replaced Hume on the left.
But the Dons did have a lifeline soon after, as Conor Grant combined with Holland to tee-up Eisa, who found the target from close range.
The visitors’ confidence had visibly risen and there was a nervy moment when Holland slip the ball into the mixer, with Robertson keeping his cool to get it to safety.
A double switch followed from Cowley, as Swanson and Mingi made way for Koroma and Ryan Tunnicliffe.
The visitors were still threatening, however, and a scramble in the box led to Louie Barry’s strike being beaten away by Griffiths.
And the Blues saw out six minutes of stoppage-time to ensure they would be in the hat for Monday night’s third round draw.
Pompey (3-4-1-2): Griffiths; Morrison, Raggett, Robertson (c); Swanson (Koroma 81), Mingi (Tunnicliffe 81), Pack, Hume (Ogilvie 59); Hackett; Bishop, Curtis
Goals: Hackett 22, Bishop 35 (pen), 48 (pen)
Subs not used: Oluwayemi, Quarm, Dockerill, Payce, Mottoh, Pigott
MK Dons (4-2-3-1): Cumming; Watson (Lawrence 82), Tucker, O’Hora (c), Harvie; McEachran (Grant 46), Johnson (Robson 71); Burns (Barry 69), Devoy, Holland; Eisa (Grigg 82)
Goals: Burns 19, Eisa 61
Booked: McEachran, Lawrence
Subs not used: Ravizzoli, Jules, Oyegoke, Dennis
Referee: Sunny Gill
Attendance: 8,056 (203 away fans)