Connacht started well and the few supporters they bought with them were given hope they would make it two wins on the trot.
Outside half Tim Donnelly gave the visitors an early boost with a 5th minute penalty from 35 metres. But the Scarlets finished the half strongly with Regan King getting a try and Rhys Priestland kicking eight points for a 13-3 interval lead.
Donnelly again gave Connacht hope with another 35 metre penalty six minutes after the restart. However, the Scarlets wrapped up the issue with tries from Vernon Cooper and Morgan Stoddart.
Connacht battled to the end and John Fogarty got in for a late try. However, the home side sealed a bonus point when Jonathan Davies got their fourth try in stoppage time.
Tries: King, Cooper, Stoddart, J Davies
Cons: Priestland (4)
Pens: Priestland (2)
Pens: Donnelly (2)
Scarlets: M Stoddart, G Evans; R King, G Evans, M Watkins, R Priestland, G Cattle; P John, J Hayter, B Broster, V Cooper, A Eustace, D Jones, J Bater (capt), N Thomas
Replacements: I Thomas, K Owens, L Reed, J Edwards, D Manu, L Davies, J Davies
Connacht: P Durcan; O Treviranus, M Deane, A Wynne, D Yapp; T Donnelly, C McPhillips; B Wilkinson, A Flavin, capt, R Morris, M Swift, D Gannon, M McCarthy, J O'Connor, C Rigney
Replacements: J Fogarty, R Loughney, J Muldoon, R Ofisa, C O'Loughlin, K Matthews, D Riordan
Referee: Andy Macpherson (SRU)