The Dragons avenged two early-season defeats against the Scarlets to move clear of their Welsh rivals near the top of the Celtic League table.
Dragons (9) 15:
Pens: Montgomery 5.
Scarlets (3) 9:
Pens: Bowen 3.
Former Springbok Percy Montgomery kicked all 15 of the Dragons' points, winning the kicking duel with Scarlets fly-half Gareth Bowen.
Bowen had three penalties to his name as the visitors claimed a bonus point for losing by less than seven points.
The result preserves the Dragons' unbeaten Celtic League home record.
In fact the only blemish for Mike Ruddock's side at their Rodney Parade stronghold this season is a loss against Leicester in the Heineken Cup.
The Scarlets had more international stars on RBS Six Nations duty than their hosts, but still had key players Scott Quinnell, Mark Taylor, skipper Vernon Cooper, John Davies and Barry Davies in their ranks.
Montgomery kicked the Dragons into a 9-0 lead but Bowen got the visitors on the score-sheet with a penalty in first-half injury time.
The visitors had their best try opportunity five minutes after the break when Quinnell was held up over the line.
It was left to Bowen to draw the Scarlets close at 9-6, then again to 12-9 after swopping penalties with Montgomery.
Big-name signing Bob Skinstad came on after 50 minutes into the home side's back row.
But it was the Dragons' other Springbok, Montgomery, who caught the eye and made the game safe, kicking his final penalty three minutes before time.
Although neither side managed a try it was thrilling end-to-end stuff, with the Scarlets coming off second best for the second week running following their
defeat in Ulster last week.
Dragons: S Tuipulotu; N Brew, P Montgomery, A Marinos (capt), B Breeze; C Warlow, G Baber; A Black, S Jones, C Anthony, I Gough, P Sidoli, J Ringer, J Forster, S Van Rensburg.
Replacements: P Young, R Snow, N Edwards, B Skinstad, R Jones, L Jarvis, H Luscombe.
Scarlets: B Davies; R Rees, M Taylor, M Watkins, T Selley; G Bowen, M Phillips; P John, A Gravelle, J Davies, V Cooper (capt), A Jones, D Hodges, G Williams, S Quinnell.
Replacements: I Thomas, A Yelland, C Wyatt, E Lewis, D Burn, C Thomas, D Rogers.
Referee: Malcolm Changleng (Scotland)