Goals from James Bolton and John Marquis ensured Pompey won at Fleetwood to reach the fourth round of the Emirates FA Cup for a second successive season.
There was little to separate the League One promotion hopefuls before the break at a chilly Highbury Stadium.
But the visitors were more clinical in a rain-soaked second half and James Bolton arrived at the far post to open his Blues account.
John Marquis added a second in similar fashion soon after and Conor McAleny’s stoppage-time effort proved no more than a consolation.
Kenny Jackett made three changes from the side that collected a point at Gillingham on New Year’s Day.
Loan signing Steve Seddon went straight into the starting line-up following his arrival from Birmingham on Thursday.
There were also returns for both Marquis and Andy Cannon, with Gareth Evans, Ben Close and Ellis Harrison dropping to the bench.
With Seddon slotting in at left-back, the versatile Anton Walkes moved up to join skipper Tom Naylor in the midfield engine room.
The game – as with all third round fixtures – began one minute late to give everyone the chance to think about looking after their mental health.
There was an early chance for the visitors once the action started, with Bolton looping a header narrowly wide following good work down the left by Marcus Harness.
Marquis then cried for a penalty after going down in a challenge for the ball with Ashley Eastham, although referee Marc Edwards ignored his appeals.
It was generally a slow opening to the contest, however, with neither keeper being called into action.
There were fears for Wes Burns when a clearance from Seddon smacked into his head from point-blank range, but the winger was quickly back on his feet.
On a cold evening on the Fylde coast, there were only half-chances to excite the travelling fans, with a fierce volley from Cannon fizzing not too far off target.
But the action intensified as time progressed and a passage of patient passing play from Pompey ended with the lively Harness drawing a save from Alex Cairns.
Paddy Madden’s effort was then comfortably stopped by Alex Bass at the other end, while an attempt from Marquis was blocked by Harry Souttar.
The quick feet of Harness were causing problems for the hosts and after racing across the six-yard box, he could only find the side netting.
Fleetwood were seeing plenty of the ball, but not really testing Bass, although a Josh Morris free-kick was diverted narrowly over his own bar by Marquis.
The visitors won a set-piece themselves before the break and Seddon’s delivery was nodded off target by Sean Raggett.
Half Time: Fleetwood 0 Pompey 0
The rain was falling when the sides returned after the break, but clear-cut openings continued to be at a premium.
Bass dealt with a dangerous Burns cross, while Christian Burgess’ block denied Cod Army left-back Danny Andrew.
It then took a perfectly-timed challenge in the box from Harry Souttar to stop Cannon from Converting Marquis’ threaded pass.
The contest was lacking quality in the final third, although a delivery from the impressive Harness caused problems as it bounced around the box before being hacked clear.
And another cross – this time from Curtis – led to the Blues finally breaking the deadlock on 66 minutes.
Fleetwood failed to deal with the danger and the ball appeared to get flicked on inside a packed box before BOLTON bundled it over the line from a yard out.
There probably should have been an immediate leveller, but an unmarked Madden scooped high over the bar from Burns’ cut-back.
Pompey quickly made them pay, as Seddon’s corner was headed powerfully back across goal by Burgess and MARQUIS converted at the back post.
The hosts were trying to find a route back into the tie, but some more wasteful finishing from Madden was proving costly.
Seddon was replaced by Close – making his 150th Blues appearance – late on, as Jackett introduced some fresh legs.
Fleetwood were given hope in stoppage-time, as a strike from substitute McAleny took a deflection to beat Bass.
That caused hearts to flutter in the away end of Highbury, but the Blues saw out the closing stages to secure their progress.
Fleetwood (4-4-2): Cairns; Coyle, Eastham (McAleny 83), Souttar, Andrew; Burns, Coutts (c) (Sowerby 72), Dempsey, Morris; Madden (Saunders 81), Evans
Goals: McAleny 90+1
Subs not used: Gilks, Hill, Biggins, Garner
Pompey (4-2-3-1): Bass; Bolton, Burgess, Raggett, Seddon (Close 81); Naylor (c), Walkes; Harness, Cannon, Curtis; Marquis
Goals: Bolton 66, Marquis 72
Booked: Raggett, Walkes
Subs not used: MacGillivray, Downing, Evans, Hawkins, Pitman, Harrison
Referee: Marc Edwards
Attendance: 2,145 (525 Pompey fans)