Despite two exquisite tries by a couple of Ireland hopefuls, Craig Gilroy and Luke Marshall, Ulster, who were top of the pile last week, made too many errors to see off their welsh rivals who again made good use of the width of the Ravenhill pitch with a neat brand of exciting rugby.
Maybe it was the gaudy orange and yellow jerseys of the visitors, but Ulster at times appeared to be like scared rabbits in headlights.
They have been poor since Christmas and although they still managed to top the league for a couple of weeks, they failed to really hit the seat spot.
With missed tackles, a lack of composure and patience in the red zone being deciding factors, Ulster never really looked comfortable even when in the lead.
They were also just a tad too nice at the breakdown where Scarlets gave nothing away.
Scarlets shot into the lead as early as the fifth minute when they negotiated a simple four-to-one overlap on the left after a missed tackle in midfield, and full-back Michael Collins had the simple task of running in unopposed from 22 metres.
The visitors, who always looked dangerous when getting quick ball from the breakdown, extended their lead on 10 minutes with Aled Thomas popping over a penalty.
That was immediately matched by dropped goal by Jackson as Ulster belatedly fired up their engine, and showing a newly-acquired off-loading game.
It was a dynamic try by Craig Gilroy in the 20th minute that saw Ulster forge ahead.
A brilliantly-worked wrap-around decoy running amongst the Ulster backs saw Luke Marshall set Gilroy free and the left wing kicked over Collins and collect the bounce to go over with Jackson converting from the touchline.
However, the lead was short-lived with Scarlets again easily finding space on the left. Collins again had time and space to dot down with Thomas adding the extras.
It was yet another superbly-taken try that saw Ulster go in at the break with a 17-15 lead. It was the Marshall duo who started and finished the move.
Scrum-half Paul broke through in midfield, gave centre Luke the ball and the Ireland centre pinned his ears back from 35 metres and dived over. Jackson again banged over the conversion.
Two quick-fire penalties by Thomas saw Scarlets draw first blood on the restart when Ulster’s shaky defence was at the heart of the problem.
A yellow card for flanker Chris Henry didn’t help matters, but Ulster managed to keep the score at bay and a Jackson penalty in the 64th minute got Ulster within a point. Despite a lot of huffing and puffing, Ulster just could not prise open the Scarlets defence as the visitors hung on for a rare success at Ravenhill.
(Gilroy Marshall tries; Jackson drop goal, penalty, 2 cons)
S Olding, C Gilroy, D Cave (Arnold, 60), L Marshall, J Stockdale, P Jackson (capt), P Marshall (Pienaar, 60); A Warwick (McCall, 46), J Andrew (Murphy, 46), R Lutton (Ross, 46), A O’Connor (Browne, 25), F van der Merwe (Reidy, 71), R Diack, C Henry, R Wilson.
(Collins 2 tries, Thomas 3 penalties, con)
M Collins, G Owen, R King, H Parkes (capt), DTH van der Merwe (Owens, 41), A Thomas (Jones, 63), A Davies (Williams, 49), P John (Evans, 46), K Myhill (Elias, 63), P Edwards, G Earle (Paulino, 54), D Bulbring, A Shingler (Pitman, 54), W Boyde, M Allen.
I Davies (WRU)