Stephen Ferris returned after a 15-month absence to help Ulster secure a 26-13 bonus-point win over Scarlets.
Paddy Jackson scored two tries in an impressive first half while Tommy Bowe added a third try for Ulster.
Gareth Davies touched down for Scarlets as Ulster led 21-10 at the break with Ferris making his long-awaited comeback from injury in the second half.
Olly Barkley's penalty reduced the gap before Tom Court went over in the final seconds for the bonus point.
Scarlets failed to take advantage of a stiff breeze at their backs, with Ulster holding a commanding 11-point lead at the break.
Jackson was the inspiration for the hosts in the first half with two tries and setting up the other.
There was a touch of fortune for the opening try on 15 minutes, a bad bounce deceiving Aled Thomas with Jackson snapping up the loose ball and going over.
The fly-half burst through a gap three minutes later before his pass gave Bowe the simple task of running in from 10 yards.
Ulster prop Callum Black was stretchered off with an ankle injury before Olly Barkley slotted over a penalty for the visitors.
Roles were reversed for Ulster's third try after 34 minutes with Bowe making the break and a deft pass put in Jackson, who touched down before Ruan Pienaar scored his third conversion.
The Welsh side hit back two minutes later when Davies raced on to his own kick, and the scrum-half outpaced Pienaar to tap down for the try.
Barkley converted but the centre pushed a penalty wide with the last kick of the half.
Pienaar missed two penalties in an error-strewn opening 20 minutes of the second half, as the intensity went out of the game.
That changed when Barkley slipped over his second penalty to reduce the deficit to eight points.
The biggest cheer of the night came on 63 minutes when Ferris was brought on for his first appearance since November 2012 after an ankle injury.
The Ireland flanker made an immediate and trademark impact, driving Jordan Williams back 15 yards after the full-back caught a high ball.
Pienaar was forced off with a wrist injury before Ulster's late pressure paid off when Court rumbled over from close range, the last-gasp bonus-point try awarded after replays by the TMO.
Jackson missed the conversion but the bonus-point was secured and Ulster moved to within three points of second-placed Leinster and four behind leaders Munster, while Scarlets remain in sixth.
Ulster: Payne, Bowe, Cave, McCloskey, Scholes, P. Jackson, Pienaar, Black, Herring, Afoa, Muller, Diack, Wilson, Doyle, Williams.
Replacements: Court for Black (25), Gilroy for Bowe (63), R. Andrew for Scholes (74), Heaney for Pienaar (77), Annett for Herring (48), Lutton for Afoa (70), Stevenson for Diack (74), Ferris for Williams (63).
Scarlets: J. Williams, K. Phillips, Maule, Barkley, Climo, A. Thomas, G. Davies, John, Myhill, Adriaanse, Earle, Snyman, Turnbull, Barclay, McCusker.
Replacements: Lewis for Maule (70), R. Evans for Climo (65), A. Warren for John (65), Kelly for Earle (74), Timani for McCusker (47). Not Used: E. Phillips, Lee, A. Davies.
Referee: Neil Hennessy (WRU)
Assistant Referees: Gary Conway, Gary Glennon (both IRFU)
Citing Commissioner: Wayne Sheridan (IRFU)
TMO: Marshall Kilgore (IRFU)