A stylish, confident and attacking opening half at Parc y Scarlets – arguably the best of the season - was rewarded as Lloyd Williams and Tom James went over for tries.
The accurate boot of Dan Jones and Aled Thomas kept Scarlets within range all afternoon as they kept the scoreboard ticking over with penalties.
However, fly half Gareth Anscombe scored a superb third visiting try, after a quite audacious dummy close to the line sent him over, to secure the points.
And even a late try from Scottish back row John Barclay and frantic finale, with Josh Turnbull yellow carded, could not deny Danny Wilson’s men as they deservedly completed the double over Scarlets.
The morning gloom had broken by the time the two sides entered the field and an early penalty for accidental offside gave Scarlets a platform in the opening minutes. But the all-action Taufa’ao Filise rocked Ken Owens back with a thundering tackle before the visitors won a penalty.
The big prop was prominent in the early stages as he rattled down the middle and offloaded in the tackle to spark a first attack from Cardiff Blues deep inside their own 22.
A neat chip into space by Anscombe was collected by DTH van der Merwe, but he then spilled under pressure and allowed Rhys Patchell to kick into space and force Gareth Davies to carry the ball over for a five-metre scrum to Cardiff Blues.
A penalty for not releasing, after a series of drives around the fringes, then gave Anscombe a simple kick from in front for the lead after nine minutes.
A slicing break from deep from Tom James and Rey Lee-Lo caused more home alarm and it was scrum half Lloyd Williams who took full advantage to burst free to race over for the game’s first try and a 10-0 lead.
Scarlets hit back three minutes later with a penalty from Dan Jones, after Cardiff Blues were penalised at the breakdown, before another kick saw the lead cut to four points at the mid-point of the half.
Lee-Lo looked a dangerous runner from deep as he again made yards down the right flank before slick hand from James, Patchell and Williams opened up space for Anscombe.
His flick pass sent Fish just inches from the line before patient approach play opened up space for James to bulldoze over the final man and score a second away try.
Cardiff Blues looked threatening from deep with more sweet handling freeing up Garyn Smith to James, but his time the winger just failed to hold on under pressure from his opposite man.
Scarlets again cut the lead back with a penalty from Jones, after a scrum penalty on visiting ball.
A big driving maul drew some success for Cardiff Blues in the final minutes of the half before strong forward work inside the home 22 secured a penalty and Anscombe nudged it over.
Back rowers Warburton and the impressive Jenkins then combined to win a penalty as Scarlets were repelled as they looked to finish the half strongly.
Scarlets kicked tactically well at the start of the second half as they looked to pin the visitors back inside their own 22 and force errors. But a superb grubber kick from Williams, after Jenkins unloaded a huge tackle, eventually forced the home side back.
A succession of penalties against Cardiff Blues from the whistle of Italian referee Marius Mitrea saw Jones cut the lead back to 18-12 after 47 minutes.
Solid work from Warburton turned over ball and then his snagged Gareth Davies at the back of a lineout before a charged down clearing kick forced a penalty and Anscombe did the rest.
But the good work was undone when a needless penalty at the next breakdown allowed replacement Aled Thomas to confidently strike over his first points of the game.
Patchell saw a penalty attempt from just inside halfway drift wide right of the target on the hour.
A superb third try, though, then arrived when the bustling James broke the line and fed the ball inside to the supporting Anscombe who drew the final man and delivered a delicious dummy before coasting over.
Cardiff Blues looked to play the final 20 minutes in the home half with Williams putting in some testing box kicks and Anscombe looking to control territory.
A breakaway from replacement scrum half Aled Davies saw Scarlets rally and a penalty saw them kick to the corner.
And a scrum against the head suddenly created a lifeline as Barclay was shunted over with the Cardiff Blues defence splintered and exposed with eight minutes left.
Another charged down kick, this time Williams on Davies, pinned Scarlets back inside their own half. But a lost lineout created more home ball as the noise inside Parc y Scarlets cranked up a level.
A groggy Patchell was replaced by Summerhill while tempers flared off the ball and Turnbull was yellow carded after referee Mitrea consulted with his touch judge.
Summerhill and Williams combined to fire into the home 22 before solid defence on Steffan Evans stopped the wing and dragged him into touch as pulses continued to climb.
And it was Cardiff Blues who remained composed in the closing minutes to run the clock down before scrum half Williams kicked out the ball to end an absorbing contest.
Timeline:
09m Anscombe p 0-3
11m Williams t Anscombe c 0-10
14m Jones p 3-10
17m Jones p 6-10
24m James t 6-15
30m Jones p 9-15
37m Anscombe p 9-18
47m Jones p 12-18
54m Anscombe p 12-21
56m Thomas p 15-21
63m Anscombe t Anscombe c 15-28
71m Barclay t Thomas c 22-28
Cardiff Blues: 15 Rhys Patchell (Summerhill 75), 14 Dan Fish, 13 Garyn Smith, 12 Rey Lee-Lo, 11 Tom James, 10 Gareth Anscombe, 9 Lloyd Williams; 1 Gethin Jenkins (Thyer 72), 2 Matthew Rees (Dacey 39-40, 58), 3 Taufa’ao Filise (D Lewis 72), 4 Josh Turnbull, 5 James Down (Hoeata 56), 6 Sam Warburton, 7 Ellis Jenkins, 8 Josh Navidi
Replacements: 16 Kristian Dacey, 17 Brad Thyer, 18 Dillon Lewis, 19 Jarrad Hoeata, 20 Manoa Vosawai, 21 Lewis Jones, 22 Jarrod Evans, 23 Aled Summerhill