A riveting match began with the Seagulls playing catch-up after Portsmouth went ahead in under three minutes at Fratton Park.
But it was a challenge Martin Hinshelwood's men quickly lived up to.
Pompey's goal on just 2 mins 53 sec was superbly crafted by Merson.
The former Arsenal and Aston Villa maestro chipped a delightful pass through to Taylor, advancing through the inside left channel.
Taylor's low angled drive across Petterson from 15 yards found the far corner of the net with chilling accuracy.
Albion responded positively to the early blow and almost equalised after five minutes.
A diagonal ball towards the area from Butters was headed by Marney into the path of Brooker.
The left winger nodded the ball over the onrushing Hislop and narrowly wide of the target.
The storming start continued as Albion pulled level after eight minutes with a move initiated and finished by Cullip.
He fed Barrett and when the new boy's effort was blocked it fell for Cullip to sidefoot in left-footed from 12 yards past Hislop and a couple of defenders.
Cullip's swift riposte ended an Albion goal famine spanning six hours and 40 minutes since Bobby Zamora's clincher in the opening day victory at Burnley.
It was also the Seagulls' first goal in six visits to Fratton Park stretching back to 1985.
Pethick covered well when Todorov tried to burst between defenders inside the box.
Both sides were looking bright and lively going forward and the respective defences were being stretched.
Carpenter tried his luck from long range. The shot was crisply struck but straight at Hislop.
Burton went down rather too easily in the Albion area for the liking of referee Steve Bennett, taking charge of an Albion match for the second time already this season.
The home fans yelled for a penalty, but instead Burton received a ticking off for diving.
The Seagulls stunned the table toppers by taking the lead with a gift in the 19th minute.
Hughes, the ex Bournemouth midfielder, tried to find Hislop with a back pass.
He was left holding his head in his hands as Brooker nipped in to slip his second goal of the season past Hislop from 12 yards.
Pompey, who had not conceded a goal in their previous two home games, were clearly rattled by Albion's sensational recovery.
Barrett's movement and tenacity was giving the home defence plenty to think about and Pethick was only just too high from 30 yards as the Seagulls' confidence soared.
There was no let-up in the action as Portsmouth got back on terms in the 26th minute.
Referee Bennett decided Butters had wrapped his arms around Burton when the Portsmouth forward had his back to goal from Taylor's left wing centre.
The Orpington official pointed straight to the spot and Merson calmly stroked home his second penalty in as many home games, sending Petterson the wrong way.
It was mouthwatering stuff for the fans, including 3,000 cheering on Albion from behind Petterson's goal at the Milton end.
Portsmouth pressed for a third and Cullip made an important block to deny Todorov when Burton headed a cross from the irrepressible Merson into the path of the ex Celtic striker.
Petterson was alert to the danger when Taylor tried to catch him napping with a quickly taken free-kick towards the top corner of the net from 25 yards.
Albion's keeper held the ball beneath his crossbar before demonstrating a safe pair of hands again from Quashie's low 25 yarder.
Portsmouth, with Merson pulling the strings, were scintillating when they attacked.
Cullip was having an outstanding match to keep them at bay. He came to the rescue with a wonderfully timed tackle on Quashie just outside the area after the Pompey midfielder had dispossessed Melton.
Cullip could do nothing a few moments later when Todorov cut inside him as Albion looked in vain for an offside flag.
Todorov, just six yards out, seemed sure to score, only for Petterson to block the shot with his legs at the expense of a corner.
Crowe, along with Quashie the only survivors from Portsmouth's team last season, was foiled by another fine stop from Petterson approaching the interval.
The right wing back's 25 yarder was bound for the top corner of the net when Petterson made a flying save at the expense of another corner.
Albion fell behind again in the final minute of a rousing half.
Quashie's diagonal ball from the right flank was picked up by the marauding Taylor.
He crossed low and square for the unmarked Todorov to slot in the simplest of finishes from point blank range.
Cullip and Albion assistant Bob Booker protested to referee Bennett as the players walked off at half time.
Cullip was then involved in an angry exchange with team-mate Pethick, who he presumably felt was at fault for giving Taylor so much space to supply the third goal.
The second half started in bright sunshine with Albion on the attack. Portsmouth, for all their attacking flair, were looking vulnerable at the back, which may find them out as the season progresses.
But Albion's deficit doubled on 52 minutes and they were entitled to feel a little hard done by once more.
Carpenter complained to referee Bennett about the award of a free-kick to Portsmouth midway inside their own half.
They broke smartly and Crowe cut inside to beat Petterson with a delicious left foot curler from 20 yards.
Crowe's third goal of the season gave Pompey a grip on the game and left Albion facing an uphill battle to avoid a fourth defeat on the trot.
Hughes' nightmare continued with the first caution of the contest on 53 minutes for a foul on the diligent Barrett.
Butters had his name taken on the hour for holding Todorov. It was a carbon copy of the offence for which referee Bennett awarded Portsmouth their match-turning penalty, only this time it was ten yards outside Albion's area.
Todorov had a shot from 12 yards saved by the impressive Petterson, then Oatway was booked for a foul on the marauding Crowe.
Portsmouth made a double substitution on 65 minutes, introducing Burchill for Burton upfront and Harper for Crowe on the right.
Foxe and Quashie increased the yellow card count in the space of two minutes for fouls on Barrett and Oatway respectively.
Albion brought on Pompey fan Wilkinson for Melton with 17 minutes remaining. Wilkinson had only been on for two minutes when he was booked for a foul on Quashie.
Barrett's Albion bow was dramatically cut short on 76 minutes with a red card after a scuffle just inside the Portsmouth area with Taylor.
Referee Bennett consulted with his assistant before dismissing Barrett and booking Taylor.
Albion were entitled to feel aggrieved yet again that the players involved had not been punished in the same way.
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