Scarlets outplayed Cardiff Blues to secure their second bonus-point win in the LV= Cup to move top of Pool Three.
Tries from Adam Warren, Kirby Myhill, Richie Pugh and Kieran Murphy earned the visitors their resounding victory,
Fly-half Aled Thomas converted two of the tries and was successful with two penalties.
The home side's only points of the game came during the first half from a Rhys Patchell penalty.
The visitors took an early grip of the game with Warren crossing for a try after two minutes before Myhill added a second on 18 minutes.
Scarlets had to wait until the second half for further tries with veteran flanker Pugh forcing his way over from short range.
And they secured the bonus point with five minutes remaining when number eight Murphy crossed for their fourth try of the afternoon.
Cardiff Blues: Fish; Mustoe, A Thomas, Allen, Robinson; Patchell, Downes; Trevett, Tyrell, Harford, Hill, Down, Navidi, Shellard, Hamilton.
Replacements: O Williams for A Thomas (36), L Williams for Robinson (54), Breeze for Tyrell (69), Corsi for Harford (56), Screech for Hill (58), E Jenkins for Shellard (72).
Not Used: T Davies, L Jones.
Scarlets: Evans; L Williams, Lamont, Warren, Ford; A Thomas, G Davies; John, Myhill, Gardner, Timani, Welch, Gilbert, J Edwards, Murphy.
Replacements: Newton for Evans (63), L. Rees for Ford (48), R Williams for G. Davies (55), R Jones for John (40), Phillips for Myhill (40), R Thomas for Gardner (14), Day for Welch (55), Pugh for Gilbert (58).
Ref: Greg Garner (RFU).