The Scarlets clung on to make it two out of two, and nine points out of a possible ten, to lead the way in Pool 5 of the Heineken Cup...
The home side got off to a flying start and scored their first try within three minutes after Regan King had regathered his own charge down on opposite number Paul Steinmetz' kick ahead.
That opportunist try was almost followed by another eight minutes later when Wales wing Mark Jones took an inside pass from namesake Stephen.
Jones managed to cross the line but lost the ball in the tackle, and referee Tony Spreadbury awarded an Ulster scrum instead of a try, after consulting with the video ref.
Stephen Jones increased the Scarlets' lead with a 27th minute penalty, but two penalties in the space of two minutes from the ever accurate David Humphries cut the deficit to two points before Jones sent his side into the interval 11-6 ahead with a penalty from the last kick of the half.
Having started the first half so badly, Ulster were the dominant force in the opening exchanges in the second half. Humphrys kicked his third penalty and the visitors looked ready to cause an upset.
The Scarlets conjured up a second try for wing Mark Jones that went through nine phases and 26 pairs of hands before he crossed the line.
Stephen Jones' touchline conversion looked to have put some distance between the two teams, but Ulster refused to give up and two more Humphries penalties got them back to within three points after 64 minutes.
Another Jones penalty gave the Scarlets some breathing space, but Ulster could have grabbed a try to win the game from a driving maul. They got up to the line, and looked set for the try, but Isaac Boss bumped into man of the match Neil Best, the ball went loose, and Gavin Thomas gleefully scooped it up to allow the home side to clear.
RGC 1404 have celebrated their crowning as Division One East winners, after just one season of competitive rugby. A big crowd turned out to support the clubs 'Celebration Saturday' when they were presented with the SWALEC trophy following their definitive 45-0 home win against Rhydydfelin on 18 May.
A special video package as Pontypridd claimed the double for the first time in their history by winning the Principality Premiership final, including match build-up, highlights, post match reaction and dressing room celebrations.