The Welsh All Blacks outscored the Wizards by three tries to one, captain Gareth Gravell crossing for a brace, but the second half turned into a shoot-out between fly-halves Dai Langdon and Jamie Davies.
The two kickers went tit-for-tat but although Neath saw two players sin binned, they held on for a 27-22 win.
Neath had led 14-10 at the break, Gravell exchanging scores with Aberavon's Matthew Jenkins. And although Gravell added a second and Dafydd Howells also crossed, they weren't out of sight.
The sin binning of Chris Morgans and Howells only hindered them but although Davies kept Aberavon in it with the boot, the Welsh All Blacks held on.
Langdon and Davies had exchanged penalties in a cagey opening but when the first chance arrived, it was Neath who created it.
Fly-half Langdon chipped through and when Jon Griffiths collected with Howells outside him, he looked odds on to score. But when the covering Aberavon tacklers arrived, a big hit forced the Neath lock to knock on in the tackle and the chance was lost.
The try may not have arrived but Neath were having the better of the territory and with Aberavon struggling to control their discipline, a pair of Langdon penalties soon extended his side's lead to 9-3.
It then got better when Neath skipper Gravell emerged from a huge forward drive to score the first try of the day. Langdon missed the conversion but his side were now comfortably ahead.
With an 11 point deficit, the Wizards needed to strike back and they thought they had done just that when Richard Carter cantered through. With options left, Davies flung a brilliant inside ball to the Aberavon wing who raced clear to score. Sadly for those in red and black, referee Sean Brickell pulled play back for a forward pass, a decision which divided the St. Helen's crowd.
The respective fly-halves then each put a penalty wide as there remained little between the sides. If Aberavon were perhaps a little unlucky to see Carter's try ruled out, some consolation then arrived when Jenkins went over with the last play of the first half. Davies was again the creator, his short ball finding Jenkins on a lovely line. The Aberavon centre, who has been so impressive in recent weeks, collected and brushed off the Neath tacklers to score to the left of the posts. Davies converted as Aberavon trailed by four at the break.
After a poor end to the first half, Neath started the second with a bang as another huge forward surge took them over the Aberavon line. It was that man Gravell who emerged with the ball to score both his and his side's second try.
Langdon missed the conversion and when Davies responded with three further penalties in quick succession for Aberavon, the game was locked at 19-19.
Inspired by Davies, the Wizards had got themselves back into it but within seconds of drawing level, they were then behind.
Wales U18 captain Howells collected a chip through following an Aaron Bramwell break as the non-stop action continued. Langdon missed the conversion but kicked a fourth penalty before Neath scrum half Chris Morgans was yellow carded by Brickell.
The nerveless Davies took advantage and with a man advantage, the Wizards knew they had to strike. They thought they had done so when following a kick through, Howells cynically brought down an Aberavon attacker and joined Morgans in the bin. Brickell decided against awarding a penalty try, instead giving Davies another chance to narrow the deficit.
He put the kick wide though as Neath, despite being down to 13 for a period, held on to reach the final.