|Guinness Pro14: Ulster v Scarlets|
|Ulster (9) 27|
|Tries: Stockdale, Andrew Con: Lealiifano Pens: Cooney 4, Lealiifano|
|Scarlets (3) 20|
|Tries: McNicholl, Davies Cons: Halfpenny (2) Pens: Halfpenny 2|
Ulster twice came from behind in a lively second half against Scarlets to secure a third successive Pro14 win.
The home side led 9-3 at the interval with John Cooney's fourth penalty stretching their lead before a frantic final half hour at Kingspan Stadium.
Scarlets twice went in front through Johnny McNicholl and Jonathan Davies tries but Ulster responded through Jacob Stockdale and John Andrew.
The win over last year's champions puts depleted Ulster top of Conference B.
Scarlets arrived in Belfast as favourites and in form after scoring 13 tries in two competitive outings this season.
They began brightly and were utterly comfortable with the ball in hand, Leigh Halfpenny's fourth minute penalty giving them a deserved lead.
However Ulster, missing the injured Marcell Coetzee, Jean Deysel, Charles Piutau and Craig Gilroy, eroded their momentum with Cooney and Christian Lealiifano dictating the terms and playing the game in the right areas.
The home side dominated territory and after a deliberate knock-on, Cooney levelled the scoring at 3-3 after 19 minutes.
Hadleigh Parks saved Scarlets with a try-saving tackle to rip the ball out of Matty Rea's hands and the visitors' defence held up well again when Louis Ludik was held up short of the line.
Cooney nailed a second penalty to put Ulster ahead for the first time and swiftly added a third after a good counter-attack to lead 9-3 at the break.
Ulster Lions not on show
The IRFU's player management policy meant the Ulster fans were not able to see their British and Irish Lions in action at Kingspan Stadium.
Scarlets included three Lions in their side, Ken Owens and try-scorer Jonathan Davies making their first starts of the season, alongside fellow tourist Leigh Halfpenny.
Ulster's Lions trio Iain Henderson, Jared Payne and Rory Best were given a watching brief, though skipper Best is facing a six-week lay-off after sustaining a hamstring injury on Thursday.
Cooney's fourth penalty of the evening stretched Ulster's lead to 12-3, but Halfpenny ended a 54-minute scoring drought for Scarlets with a routine penalty when Ulster knocked on bringing the Welsh region to within a converted try.
Despite living off scraps, Scarlets pounced on a handling error by Ulster to score the game's opening try through Johnny McNicholl in the 61st minute which sparked a flurry of tries.
Parks' side-step released Rhys Patchell who passed to the flying winger who made no mistake with Halfpenny's conversion briefly nudging Scarlets back in front at 13-12.
Their lead lasted one minute, Jacob Stockdale bundling over in the corner after a superb break and off-load by the impressive Stuart McCloskey released Sean Reidy down the blindside.
Scarlets' ability to stretch Ulster out wide paid dividends in an entertaining second half with Steff Evans punching a big hole on the wing and he released Davies for a well-worked score.
With Cooney replaced, Lealiifano took over the kicking duties and his 72nd minute penalty levelled the scores to set up a tense finish.
It was Ulster who responded to the challenge, McCloskey again involved with an off-load to release Paul Marshall. The ball was eventually recycled out to replacement Andrew to secure an impressive victory for Les Kiss' side.
Scarlets coach Wayne Pivac told Scrum V Live:
"We came here to win and it was very disappointing. Clearly we didn't play well enough in the first half.
"We played better in the second half... took the lead and at that point should have been good enough to close the game out.
"The disappointing thing is we had the ball at 20-all, kicked it back to them and they scored the final try."
Ulster: L Ludik, A Trimble, L Marshall, S McCloskey, J Stockdale, C Lealiifano, J Cooney; K McCall, R Herring, W Herbst, K Treadwell, A O'Connor, M Rea, C Henry, S Reidy.
Replacements: J Andrew, A Warwick, R Ah You, R Diack, C Ross, P Marshall, P Nelson, T Bowe.
Scarlets: L Halfpenny, J McNicholl, H Parkes, S Williams, S Evans, R Patchell, G Davies, R Evans, K Owens (capt), S Lee, J Ball, T Beirne, A Shingler, W Boyde, J Barclay
Replacements: R Elias, W Jones, W Kruger, D Bulbring, J Macleod, J Evans, R Jones, J Davies.