Barry went top of the JD Cymru South after taking a commanding three goal lead in the first half at Jenner Park.
Town took the lead in the 26th minute after Kayne McLaggon released Liam Warman on the Barry right and he fired low past the Llanelli keeper.
Barry made it 2-0 after 35 minutes. Josh Graham’s low cross from the left was met by Kayne McLaggon, whose shot from just inside the box eluded the keeper.
McLaggon made it 3-0 just before the break, scoring from the spot when Barry were awarded a penalty for a foul on Chris Hugh.
Barry found themselves down to ten men just before the hour mark when Curtis McDonald was shown a red card for a dangerous challenge, but despite the Reds pulling a goal back through Josef Hopkins in the 75th minute, the home side held on to go top of the league.