The Scarlets fought back from 13-3 down to beat Welsh rivals Cardiff Blues in the LV=Cup at Parc-y-Scarlets.
Gareth Owen opened the scoring for the hosts, but Luke Hamilton's try and Gareth Davies' conversion and two penalties put the visitors ahead.
The hosts replied with a scrum penalty try, Owen's conversion and Liam Williams' penalty.
Aled Thomas kicked three second-half penalties after the break to one by Blues fly-half Davies.
Scarlets: Liam Williams, Kristian Phillips, Gareth Maule, Gareth Owen, Andy Fenby, Dan Newton, Rhodri Williams; Shaun Hopkins, Kirby Myhill, Samson Lee, Jake Ball, Johan Snyman, Craig Price, Johnathan Edwards (capt), Kieran Murphy.
Replacements: Emyr Phillips, Phil John, Jacobie Adriaanse, Joel Galley, Dan Thomas, Gareth Davies, Aled Thomas, Nick Reynolds.
Cardiff Blues: Dan Fish, Harry Robinson, Owen Williams, Gavin Evans, Tom James, Gareth Davies, Robert Lewis; Sam Hobbs, Marc Breeze, Ryan Harford, Macauley Cook, James Down, Luke Hamilton, Thomas Young, Andries Pretorius.
Replacements: Rhys Williams, Campese Mafu'u, Foa Filise, Cory Hill, Rory Watts-Jones, Lloyd Williams, Ceri Sweeney, Rhys Patchell.