With the Ulster side depleted by both injuries and international call-ups, Jared Payne captained the province from full-back, while Michael Allen and Chris Farrell earned the opportunity to impress at wing and centre respectively.
Ruan Pienaar moved to out-half in Paddy Jackson's absence, freeing up the scrum half berth for Paul Marshall, while Rob Herring started at hooker, supported by Lewis Stevenson and Neil McComb in the engine room.
Nick Williams made a welcome return from injury at number 8 after missing the recent victories over Montpellier and Cardiff Blues.
In truth Ulster never really got going in this RaboDirect PRO12 round 7 match, enjoying relatively little possession and suffering from a lacklustre kicking return, with Pienaar missing two from five attempts.
Swirling winds at Parc y Scarlets played havoc with early kicks in open play from both Pienaar and his opposite number Steve Shingler, although the Springbok's aim was sure enough to nudge his side into a three-point lead after Sione Timani had strayed offside.
The Scarlets responded well with a slow-burning push deep into Ulster territory which was defended stoutly by the visitors for over 30 phases until a lapse in concentration from hooker Kirby Myhill allowed the clearance.
A missed tackle from Williams on Josh Turnbull gave the Scarlets their next opportunity, the flanker making good ground before earning the penalty which Shingler dispatched.
The Welshmen continued to enjoy the monopoly of possession, eventually crossing the whitewash on 30 minutes as George Earle touched down from a rolling maul.
Shingler's conversion attempt screwed well wide of the posts, but the Scarlets were back in Ulster territory within minutes of the restart, only deprived of a second try when Phil John fumbled forward a metre from the line.
The hosts added to their tally just before the break, Aled Thomas kicking over from the right wing after Stevenson had been penalised for pulling down the jumper at the lineout.
11-3 down at the interval, Pienaar missed an opportunity to claw back three points for Ulster on the resumption but he atoned on 44 minutes with a well-judged penalty from 40 metres.
Both sides persisted in kicking for territory as the second half progressed, with precious little spectacle until Ulster began to exert a stronger hold on the game on the 55th minute mark courtesy of a pair of forceful pushes from the forwards.
James McKinney replaced Marshall at this stage, liberating Pienaar to play in his preferred scrum half role, and David McIlwaine made a brief cameo - coming on for a winded Allen before being yellow carded moments later for not releasing in the tackle as the Scarlets probed for a second try.
Thomas put over the resulting penalty to extend his side's lead to eight points with 15 minutes remaining, but with John soon penalised for standing up in the scrum, Pienaar brought Ulster back to within a score on 69 minutes.
Then a 22-metre lineout for the visitors led to another penalty for dangerous play directly in front of the posts, but the South African inexplicably sliced his kick wide of the left hand upright.
Roger Wilson followed McIlwaine into the sin-bin for a deliberate trip in the 73rd minute, before Thomas sealed the victory with his third penalty of the night.
Ulster go into the three-week November international break on the back of one of their poorer performances of the season to date, with a chance to get back to winning ways on Friday, November 22 when Edinburgh are the visitors to Ravenhill.