The Magpies, who booked their place in the last 16 of the Europa League in Ukraine on Thursday evening, added three priceless Barclays Premier League points to their haul to ease themselves six clear of the relegation zone.
For Pardew, who was sacked by the Saints in August 2010, the win - his side's third in four league games - served up a measure of revenge for November's 2-0 defeat on the South Coast, but more importantly, allowed him to start looking upwards once again rather than anxiously over his shoulder.
They fell behind to Morgan Schneiderlin's third-minute strike, but Moussa Sissoko's third goal for the club and a superb Papiss Cisse volley gave them the advantage at the break.
Rickie Lambert, a player who was given his Saints chance by Pardew, levelled five minutes into the second half, but Yohan Cabaye's 67th-minute penalty and a Jos Hooiveld own goal 11 minutes from time ensured that the points stayed on Tyneside.
It was France day at St James' Park today as Newcastle celebrated the seven-man Gallic influence within their squad, but it was an eighth compatriot who was first to make his mark on the game when Schneiderlin thumped home after Lambert had headed down Jack Cork's deep cross.
The Saints started with a high tempo as they pressed their hosts back deep inside their own half and paid particular attention to midfielder playmaker Cabaye, who was driven further and further towards his won goal by the efforts of Steve Davis and Cork.
However, Newcastle gradually forced their way into the game and might have been level with 15 minutes gone when Cisse set up Sissoko to fire a rasping shot across goal which may have been going just wide, but was too close for keeper Artur Boric not to make sure.
Cisse probably should have equalised three minutes later when the hard-working Yoan Gouffran's shot fell nicely for him on the six-yard line, but as he span, he sliced his effort well wide.
Central defender Steven Taylor saw a back-post header from a 21st-minute Cabaye corner deflected over by Maya Yoshida, but the momentum was very much with Newcastle.
They had to wait until 12 minutes before the break to restore parity, but it was worth waiting for.
Cabaye was starting to find more space and when he played a lovely ball down the line for Gouffran, the wide man twisted and turned his way past full-back Nathaniel Clyne to drill in a cross to which Sissoko applied the decisive touch.
There was better to come, however, with three minutes of the half remaining, and this time it was keeper Rob Elliot, making his Premier League debut, who was the provider.
His clearance sailed over Sissoko as he challenged for it, but sat up nicely for Cisse.
The Senegal international has been going through a difficult spell recently, but his dipping volley seared over the helpless Boruc and went in off the underside of the crossbar to rekindle memories of his glorious 13-goal streak during the second half of last season.
Pardew lost skipper Fabricio Coloccini to injury in stoppage time and sent on Mapou Yanga-Mbiwa in his place, and the newcomer found himself in the firing line within two minutes of the restart.
His foul on Lambert allowed the striker to take aim at goal from the resulting free-kick, and Elliot had to dive full-stretch to his left to save.
The Magpies failed to heed the warning and were made to pay for it three minutes later when Adam Lallana was given time and space down the right and cross for Lambert to steer home the equaliser.
Newcastle were fortunate not to fall behind within three minutes when Lambert climbed highest to meet another Lallana cross, but directed his header wide of the target.
Pardew's men were in some disarray and Elliot was relieved to see a 55th-minute effort from Lallana skid wide of the far post, but they gradually began to impose themselves once again, although without really threatening Boruc's goal.
However, they took the lead once again with 67 minutes played, although perhaps in controversial fashion.
Cabaye picked out Mathieu Debuchy with a fine ball over the top and the full-back's volleyed cross hit Danny Fox on the arm.
Referee Chris Foy pointed to the spot as Southampton's protests counted for nothing, and Cabaye stepped up to send Boruc the wrong way to make it 3-2.
Things got worse for the visitors and Fox in particular with 11 minutes remaining when Fox blasted Davide Santon's cross against Hooiveld and saw the ball fly past the helpless Boruc and into the net.