Marcus Harness’ opener was soon cancelled out by Charlie Wyke, but John Marquis restored the lead midway through the first half.
And it was Marquis who wrapped the points up from the spot on Wearside after Luke O’Nien had been sent off for a foul on Ryan Williams.
Kenny Jackett unsurprisingly stuck with the same side that eased to victory at Gillingham earlier in the week, with new signing Jordy Hiwula named among the substitutes.
And Pompey got off to a blistering start, looking threatening in the opening stages and deservedly breaking the deadlock on seven minutes.
Williams collected Callum Johnson’s throw and his pass was wisely left by Marquis for Michael Jacobs.
The summer signing fed the ball to HARNESS, who neatly slotted home his second goal in as many games at the Stadium of Light.
But the celebrations were soon cut short, as Denver Hume cut the ball back for Wyke to drill in an immediate equaliser.
The visitors were still looking dangerous going forward, though, and twice came close to restoring their lead from free-kicks.
They were both taken by Jacobs, with the first being met by a firm header from Sean Raggett that forced Lee Burge to make a fine save.
And the second was a shot that was thundering towards the roof of the net before the Black Cats keeper tipped it over.
A foul from Williams then led to some pushing and shoving on the sidelines, resulting in a yellow card for the winger.
But the Blues were back in front on 25 minutes after Harness had intercepted a loose Grant Leadbitter pass.
He threaded the ball through to MARQUIS, who calmly angled a shot right into the bottom corner of the net.
Some more dangerous deliveries from Harness and Lee Brown caused problems in the Sunderland area.
A quick break then saw Brown find Harness on the left and he cut inside before bending an effort off target.
Pompey had impressed before the break, but looked nervy at the back once the action restarted following the interval.
They struggled to deal with a couple of balls into the box, while a Hume cross was then glanced wide by Wyke.
And the visitors were dealt a blow when Jacobs was forced off injured 10 minutes into the second half.
He had initially tried to continue after receiving some treatment on the pitch, but eventually trudged off to be replaced by Ronan Curtis.
The Blues had not really threatened to add to their lead, although Williams saw a shot blocked following good work between Brown and Andy Cannon.
And the winger’s quick break up the pitch was then crudely ended by O’Nien, earning the defender a booking.
Harness soon skipped past a couple of challenges and found Brown, but the was a defender immediately on the left-back to deny him a shot.
At the other end, Tom Naylor and Cannon were unable to stop Hume’s mazy run, only for Raggett to prove an unbeatable obstacle.
Some patient build-up play from Pompey then resulted in Marquis converting a pin-point Callum Johnson delivery, only for the striker’s joy to be cut short by an offside flag.
But they were given a chance to wrap up the points when Williams burst into the box and was brought down by O’Nien.
Referee Robert Lewis pointed straight to the spot and showed the perpetrator his second yellow card of the afternoon, followed by a red.
MARQUIS stepped up to take the penalty, coolly sending Burge the wrong way to double his personal tally for the day.
And it almost got even better, with Harness’ effort beaten away by Burge, who then stopped Marquis from forcing home late on.
Sunderland (3-5-2): Burge; Willis, Wright, O’Nien; Gooch, Scowen (Grigg 70), Leadbitter (Graham 82), Power (c), Hume; Maguire, Wyke
Goals: Wyke 10
Sent off: O’Nien (two yellow cards)
Subs not used: Matthews, McLaughlin, Flanagan, Dobson, O’Brien
Pompey (4-4-2): MacGillivray; Johnson, Whatmough, Raggett, Brown; Williams, Naylor (c), Cannon, Jacobs (Curtis 55); Harness (Nicolaisen 89), Marquis
Goals: Harness 7, Marquis 25, 85 (pen)
Booked: Williams, Johnson
Subs not used: Bass, Pring, Morris, Close, Hiwula
Referee: Robert Lewis