Narberth kept their drive for a top seven finish alive on Saturday, with three late tries at the Dairyfield.
The game started brightly, but Llanharan's Chris Anderson scorned an early opportunity as he missed a second minute penalty attempt.
A minute later, however, in-form Otters winger, Daniel Gravell, intercepted a knock-on and raced down the right touchline, taking out a number of defenders on his 70-yard run, before crossing to score an excellent try, which was converted by Simon Daniel.
Both teams then missed further penalty attempts, in a very tight game, before, in the 30th minute, Otters' scrum-half, Chris Macdonald, was yellow-carded near his own line.
The Dairymen took advantage almost immediately, when number eight and captain, Colin Malone, forced his way through from a tap penalty, which was converted by Anderson.
Llanharan pushed harder to make their one-man advantage count, but the Otters' defence stood resolute.
At the start of the second half, outside-half Simon Daniel regained the lead for Narberth with a penalty, to capitalise on their territorial advantage.
The Otters did push Llanharan further and further back, but left it late to take the game beyond doubt, with three tries in the closing minutes.
The first came when Narberth were awarded a penalty on the 22. Some travelling fans shouted 'kick it', but instead Daniel tapped it and crossed for a try, which he also converted.
Nick Jones was the next to score with a nice finish from some sweeping play from a lineout, the fullback just squeezing in at the right-hand corner for an unconverted try.
Then, in injury time, that man Daniel Gravell popped up again to score his second of the day, taking his total to eight tries in the last four games.
Simon Daniel kicked the conversion from the touchline to give Narberth a handsome and deserved victory.
Narberth will face Bedwas at home tomorrow (Saturday), in what is an important clash, as the visitors are currently in sixth position, just two places above the Otters in National League division two.