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.
Saints set the tempo and Schneiderlin thumped home after Lambert had headed down Jack Cork's deep cross. The hosts 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 Yoan 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 Artur 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.
Just five minutes into the second half Adam Lallana was given time and space down the right and cross for Lambert to steer home the equaliser.
However, Newcastle 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 Boruc and into the net.