Ulster's four-game PRO12 winning run was brought to a halt following a 17-9 defeat by Llanelli at Parc y Scarlets.
Scarlets, who had drawn their last two fixtures against Racing Metro and Zebre in the Heineken Cup and the RaboDirect Pro12 respectively, were grateful for George Earle's try, while three penalties from Aled Thomas and one from Steven Shingler were enough to seal victory.
South Africa fly-half Ruan Pienaar scored all of Ulster's points as the province suffered their third league defeat of the season.
It was Pienaar who opened the scoring on the night when he made light of the nasty, swirling wind to slot the ball between the posts and put Ulster into a ninth-minute lead.
The Scarlets then enjoyed a prolonged period of pressure and strung together several phases of play on the Ulster line, but Ulster defended resolutely without being breached.
Replacement John Barclay did breach the Ulster defence with a piercing run but a good covering tackle from Paul Marshall denied the Scot a possible try.
Shingler knocked over a penalty from in front of the posts in the 22nd minute and nine minutes later the Scarlets converted their territorial dominance into further points when Earle rumbled over for his try.
The second row touched down after good work by his fellow forwards, but Shingler was unable to add the extra two points.
Flanker Barclay broke through the Ulster rearguard again soon after but Marshall managed to hold onto him in the tackle as he made a dash for the line.
An Aled Thomas penalty just before half-time increased the Scarlets' advantage to eight points.
Three minutes after the break, Pienaar missed with a long-range penalty attempt but the Springbok made no mistake with his next effort two minutes later.
Ulster replacement David McIlwaine was yellow-carded for not releasing just two minutes after coming on as a replacement and Thomas kicked the resulting penalty between the posts after 64 minutes for 14-6.
Pienaar replied with his third penalty of the game on 69 but was off-target with a straightforward kick from in front of the posts soon after.
Roger Wilson became the second Ulster player to be sin-binned after a trip in the 74th minute while a John Afoa infringement allowed Thomas to slot over his third penalty with three minutes remaining and condemn Ulster to a third PRO12 defeat of the season.