The departing Stephen Jones kicked Scarlets to Celtic League glory at a jam-packed Stradey Park.
Scarlets (9) 23
Pens: Jones 5
Ulster (9) 16
Pen: Humphreys 3
Jones, who was playing his final game in front of his home crowd, contributed 18 points as the Scarlets pipped the Irishmen to the title.
The Welshmen were completely dominant after the break with Matthew Watkins touching down.
Ulster had very little to offer out wide, with Neil McMillan scoring their only try a few minutes from the end.
Ulster mostly relied on the boot of David Humphreys, who contributed 11 points to what was really a damp squib of a performance.
The visitors did, however, start well when their lively pack gave them the platform for Humphreys to rifle over a long-range penalty in the fourth minute.
Scarlets v Ulster
There was very little room to manoeuvre on the park with both defences cutting down space.
It was left to Jones to stroke over an equalising penalty in the 14th minute.
With the atmosphere tense, Humphreys rattled over his second penalty in the 22nd minute. But that was matched by a snap drop goal by his opposite number.
The Scarlets then upped the tempo to allow Jones to kick his side ahead.
There was still no sign of a try, however, as Humphreys levelled things up again in the fourth minute of first-half injury time.
The Scarlets stepped up a gear on the resumption with Simon Easterby the driving force.
It was his charge down of Humphreys' clearance that set up another penalty by Jones.
The fly-half virtually wrapped up the game for the Scarlets when he burst through a yawning gap to set up Watkins in the 48th minute.
Jones missed the conversion but kicked his fourth penalty to push Llanelli towards the title.
Two more penalties by Jones sealed it, even though Ulster replacement McMillan plundered a try in the dying minutes.
Jones now leaves for Montferrand with a winner's medal as the Scarlets become the first Welsh side to take the Celtic League title.
Scarlets: B Davies, Evans, Taylor, Watkins, Finau,
S Jones, Phillips, I Thomas, McBryde, Thiel, Cooper, Wyatt,
Hodges, Easterby, Quinnell.
Replacements: J Davies, A Gravelle, Griffiths., D Jones,
Burn, G Bowen, L Davies.
Ulster: Cunningham; S Young, Mallon, Stewart, Topping; Humphreys, Doak; S Best, Sexton, Moore, Mustchin, Frost, Ward, N Best, Wilson.
Replacements: Shields, McCormack, Barker, McMillan, Campbell, Larkin, Wallace.
Referee: Rob Dickson (Scotland).