The difference was the boot of Glynneath centre Shaun Tennant, who opened the match with a penalty hat-trick and then converted a god try by left wing Matthew Davies after a clever break by fly half Darren Davies.
It had been Briton Ferry who led with a penalty by fly half Michael Arnold, but Glynneath were clear at 19-3 by half-time and soon afterwards added a good team try touched down by prop Clive Bowen.
Andrew Chappell came on to rouse the Briton Ferry pack and No 8 Julian Knight crossed the Glynneath line three times, though only two efforts were awarded.
The game, that was watched by Glynneath president Max Boyce and former international referee Clive Norling, ended with Kim Priddle, Field Sales Executive of Molson Coors, presenting the cup to Glynneath's wing and captain Dan Challenger.
Credit went to both sides for a good, spirited game with Glynneath deserving the win, but Briton Ferry's spirit was magnificent.