Llanelli took the lead in the fourth minute through Luke Richards' penalty before Neath ran in the first of their three tries, scrum-half Kevin Farrell bundling the ball over the line after a move on the right hand side in the tenth minute.
Neath held a slender 7-6 lead after Richards kicked a second penalty following Arwel Thomas' conversion, before Luke Ford stretched their advantage with a try on 29 minutes.
The centre received a clever switch pass from Gareth Gravell which enabled him to charge over unchallenged.
Thomas again converted and added two more penalties to give Neath a 20-6 half time lead.
The second period started slowly until a moment of inspiration from Llanelli's Aaron Schingler, who picked up the ball in his own half and furiously ran the ball home on 53 minutes.
Llanelli were back in the game, but as was the case in the first half, they could not capitalise on the opportunities were creating and ultimately paid the price.
Neath full-back Gareth King jinked through the Llanelli defence on 65 minutes to score the All-Blacks third try, and put the result seemingly beyond doubt at 27-11
With nine minutes remaining, Llanelli outside-half Richards, chased a loose ball forward and pushed it over the tryline, converting to bring the score back to 27-18 in Neath's favour, but the All-Blacks held on to lift the cup for the sixth time.