Scarlets fly-half Gareth Bowen and Blues centre Lee Thomas exchanged penalties in what proved to be a unfulfilling opening quarter for the bumper crowd, keen to prolong the Welsh Grand Slam party.
The opening try of the game arrived on the half hour when prop Phil John went over uncer the posts after some good work from No.8 Andy Powell.
The Blues bounced back when Thomas grabbed another penalty but the Scarlets rested back control of the game with another try before the break.
Powell crashed over from the back of a five metre scrum and the hosts went into the break 17-6 to the good.
The Scarlets reaffirmed their dominance after the break when Bowen added another three-pointer but the Blues once again battled back with a try from through Martin Jones when he got on the end of a drive from a line-out.
The extras came courtesy of Thomas, and he had a chance to narrow the gap even further later in the half but his effort failed with five minutes on the clock.
The result, was assured with another try for the Scarlets through skipper Vernon Cooper which prevented the Blues from gaining a bonus point.
Full-time score: Scarlets 25 (John, A Powell, Cooper try, Bowen 2 conv, 2 pen), Blues 13 (M Jones try, L Thomas conv, 2 pen)