Scarlets opened their Heineken Cup Pool 1 account with a victory as they defeated Castres 31-23 on Saturday.
It was their second-half effort that ultimately claimed the win, with internationals Stephen Jones et al starring at Parc y Scarlets.
Jones kicked three first-half penalties to opposing full-back Romain Teulet's brace, with the home side going in at the interval 9-6 to the good.
Scarlets came out from the break in good form and crossed through Scotland international Sean Lamont. Teulet responded via three points though.
However, George North then motored downfield in a move that set up his eight Ben Morgan for what became a key try in the context of the match.
Wing Marc Andreu responded with a score of his own and the metronomic Teulet added the extras to cut the lead down to just seven points.
But as the match went back and forth, Scott Williams got the Scarlets going again as he fed Wales outside centre and Scarlets inside centre Jonathan Davies for the hosts' third.
Chris Masoe did set up a nervy conclusion with a late score but when international replacement Rhys Priestland slotted a late penalty, Castres' fate was known.
Tries: Lamont, Morgan, Davies
Con: Jones 2
Pen: Jones 3, Priestland
Tries: Andreu, Masoe
Con: Teulet 2
Pen: Teulet 3
Scarlets: 15 Liam Williams, 14 George North, 13 Scott Williams, 12 Jonathan Davies, 11 Sean Lamont, 10 Stephen Jones, 9 Tavis Knoyle, 8 Ben Morgan, 7 Jon Edwards, 6 Aaron Shingler, 5 Damian Welch, 4 Dominic Day, 3 Rhys Thomas, 2 Matthew Rees, 1 Iestyn Thomas.
Replacements: 16 Ken Owens, 17 Phil John, 18 Rhodri Jones, 19 Sione Timani, 20 Richard Pugh, 21 Rhodri Williams, 22 Rhys Priestland, 23 Daniel Evans.
Castres: 15 Romain Teulet, 14 Matthieu Nicolas, 13 Paul Bonnefond, 12 Romain Cabannes, 11 Marc Andreu, 10 RÃ©mi Tales, 9 Thierry Lacrampe, 8 Iosefa Tekori, 7 Steve Malonga, 6 Chris Masoe, 5 Rodrigo Capo Ortega, 4 Matthias Rolland, 3 Luc Ducalcon, 2 Marc-Antoine Rallier, 1 Anton Peikrishvili.
Replacements: 16 Brice Mach, 17 MichaÃ«l Coetzee, 18 Karena Wihongi, 19 Scott Murray, 20 Jannie Bornman, 21 Thomas Sanchou, 22 Pierre Bernard, 23 Pierre-Manuel Garcia.
Referee: Greg Garner (England)