Although they staged a spirited second half comeback, the Athletic were unable to overhaul a 21-point interval deficit in this clash with Llangadog.
The Athletic suffered a body blow early on when prop Alan Phillips was injured, with flanker Nick Roach gamely opting to fill his place in the front row.
The back row man must have regretted his bravery later on, however, picking up a broken nose for his troubles. He was replaced by fellow flanker Dafydd Bevan.
Llangadog's tries came from Wyn Harris, Gwyndaf Thomas, Adrian Williams and Roger Everett, with wing Rhydian Davies converting two and adding three penalties.
Anthony Griffiths, Dean Roberts and Andrew George bagged a try apiece for Narberth, with Shane Higgon landing two conversions.
Narberth Athletic are without a fixture tomorrow (Saturday), but will be playing a home match against Llangennech on December 29.