The Dragons led 10-3 at the break but tries from Gareth Maule and Phys Priestland sealed a vital victory, with Priestland's 16-point personal haul proving crucial in Llanelli.
The match may have been too tight close for comfort as far as the Scarlets were concerned but head coach Nigel Davies was nevertheless delighted to see his men bounce back from a 60-point mauling at the hands of the Ospreys last time out.
"As a coach, you're always worried that result was in the back of players' minds," said Davies after the Scarlets turned things around to beat the Dragons 21-15.
"We could have disintegrated after a score like that but the boys were desperate to get back on the field and they had to show character to get a win.
"You can do all the talking you want, but you can't put anything right until you get back on the pitch.
"For us to win anything this year, we have to be able to deal with situations when we are under pressure and I'm very pleased with the way we came through."
A well-worked Wayne Evans try put the Dragons in control at the interval of a fiercely-contested battle that saw three players sin binned.
But the Scarlets refused to panic in the face of outside fears that, if Monday's hammering by the Ospreys was to be followed by a second home defeat of the campaign, their season could come crashing down in some style.
Maule gave the Scarlets the perfect start to the second period when he crossed barely a minute after the break, while Priestland controlled the remainder of the game superbly as he made light of the absence of Wales and Lions star Stephen Jones.
"I was frustrated that we were behind at half-time having dominated the possession and territory in the first half but we remained calm, didn't panic and got the early score that helped lift the team," added Davies.
"The significant moment was the series of scrums they had in our half when we were down to 14 men but I thought we dealt with that very well.
"I thought Rhys Priestland was superb with the way he ran the game and his kicking out of hand is second to none. He reads the game very well."
Neither team gave an inch at the Parc-y-Scarlets
For the Dragons, the emotions were far less festive as they were left to rue a major missed opportunity.
Having been beaten by the Scarlets at Rodney Parade earlier this term, this was a chance to gain revenge and climb the Magners League table.
To be leading at half-time and then to fall just short only enhanced the feeling of disappointment of losing one of the most-anticipated games in their calendar.
"That was one that got away," said the Dragons' Magners League ambassador Luke Charteris.
"We were confident that we could get a win here and we're pretty disappointed to only get a losing bonus point after the way the game went.
"We gave the Scarlets too much ball in the first half but really defended well to keep them out before scoring a great try right that gave us a big lift on the stroke of half time.
"We knew the key would be holding them out for the first 10 minutes of the second half but we were sloppy and let them back in the game. You can't afford to do those things, especially when you're leading away from home.
"We did really well to get back in it and showed a lot of spirit. We had the edge in the scrums but, with their backs, you can't afford any slips and that's what we did."
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