The result was welcome news to Whitland general manager David John, who is recovering in a London hospital from major heart surgery.
The Borderers dominated the opening exchanges and the match for most of the time, although the visitors took the lead through a penalty by Gareth James from 30 metres after eight minutes.
The Borderers bounced back with a penalty by Aled Davies to equalise after the young Whitland outside-half had just missed out on an ambitious penalty kick from inside his own half.
Davies increased the lead with another penalty and five minutes before the interval the lead was extended through a well worked try from fullback Gavin Morris.
Winger Andrew Jenkins had kicked ahead up the right touchline and from the consequent scrum the ball was moved along the Borderers back line. Aled Davies threw out a long pass and Morris burst into the line to cross for an unconverted try.
The second half was barely five minutes old before Morris had scored again when the Whitland backs used slick hands to switch direction from a move down the left corner into the top right corner.
The Narberth defenders had been sucked in by the initial move and Morris was able to come into the line again at pace to cross for a try converted by Aled Davies.
During the first half, the Borderers had looked sharper and more eager for the win, with the front five providing the platform for success with their work in the set-pieces.
By comparison, the Otters had often looked sluggish, but the Narberth faithful were brought back to life following a try by centre Elgan Vittle.
It had arisen from a counter-attack by substitute winger Andrew Jones, who picked up an attempted clearance kick on the left flank. He made ground with his jinking run and then centre Elgan Vittle was in support and did well to shrug off a tackle before crossing in the corner for a try which Gareth James did well to convert.
With the result in balance, the Otters pressed strongly in the closing stages, but it was all to no avail as a penalty by Aled Davies from 25 metres sealed the fate of the visitors.
Delighted with his team's success, Whitland coach Domenico Setaro, who was also celebrating the birth of his son, said: "The first half was similar to the first half in Narberth, but this time we controlled the game apart from the time when Narberth ran back at us in the second half. The scrums and lineouts went well, we approached the game in the right way and the backs supported the pack."
Rob Phillips, the new head coach of the Otters, said: "It was a disappointing result and a typical local derby where you do not get a second chance when mistakes are made. The Whitland front five put us under pressure and, although we came back a bit in the second half, we were playing catch up rugby.
"Whitland kept us bottled up and prevented us from playing our normal expansive style of rugby, so hats off to Whitland for that."
Whitland outside-half Aled Davies was nomintaed man-of-the-match at the post-match presentation ceremonies.
The match was sponsored Steve Adams, Coracle Tavern, Carmarthen, and the team sponsors were Station House,Whitland, White Horse Inn, Builth Wells, The Lobster Pot, Marloes and The Lamb, Builth Wells.
The match ball sponsors were G. D. Harries and Son, Narberth, Gog Sports, Whitland, Ken Davies Funeral Directors, Clunderwen, Dorian Phillips, Llanboidy, Ron Mounsey, McDonalds, B. H. S. (NEFF) Ltd., Gareth Morse, Zabulon, Classic Kitchens, Whitland, K. P. Thomas and Son, Templeton and David Harries, Motorfactors, Trelech.
Whitland fielded: Gavin Morris, Jack Tremlet, Lee Glanville, Mathew Hughes (Eifion Roberts), Andrew Richards, Aled Davies, Andrew Jenkins, Gareth Williams (Romeo Collella), Jason Evans, Dai Jones (Ricky Davies), Fakatah Molitika, Carwyn Davies, Johnny Koloi, Phil Morgan, capt., (Stuart Tyrie) and Randall Williams (John Bowen).
Narberth fielded: Gareth James, Daniel Gravell, Elgan Vittle, Andrew Bowen, Andy Warner (Andrew Jones), Simon Daniel, capt., Chris Macdonald (Adrian Killa), Fifipuku Falatau (Barry Davies), Kevin Allen (Craig Hawkins), Alan Phillips, Emori Katalau, Jason Jennings (David Ebsworth), Kati Tuipoluto, Mathew Evans (Lewis Woods), Gareth Bennet.