Llandovery remained in hot pursuit of first division leaders Pontypool with this hard-fought success at Parc Llwyn Ty Gwyn.
Whitland were 6-3 in front midway through the opening half but fly-half Daniel Griffiths, who had kicked all their points with two penalties, missed further opportunities and the Drovers took full advantage.
Neil Clapham was in fine form for Llandovery at full-back and second row Jamie Cudmore and loosehead prop Dorian Williams looked impressive.
Whitland had made the ideal start as Griffiths fired over a penalty. Gareth Jones responded with a kick for Llandovery but, after missing one golden opportunity, Griffiths regained the upper hand for the Boarderers with a 14th minute penalty. Griffiths and Gareth Jones both missed further chances before the Llandovery man levelled matters after the Boarderers were caught offside and a third Jones kick on target gave the Drovers a 9-6 interval lead.
Flanker Randal Williams was sin-binned just before the interval and, while Whitland were down to 14 men, the Drovers made their numerical advantage tell as Cudmore created the space for tear-away flanker Wayne Beynon to crash over for an unconverted try.
Whitland tried hard to claw their way back and in the last five minutes had a man extra as Llandovery had Lyndon Bateman yellow carded – but there was no more scoring and the visitors recorded their 14th league win in 18 games. The Beynon try was the piece of magic that Llandovery had been looking for and there was no way back for Whitland.