The league points will be scant consolation for the European defeat but the Irishmen reinvigorated their push for the top half of the table.
Marcus Horan scored the first try in only the fifth minute but all Munster could add before the break was a Ronan O'Gara penalty that left the half-time score at 8-0.
League convert Brian Carney set up Brian Murphy for the second try after collecting an O'Gara kick. The scoring was wrapped up by Anthony Foley, who powered his way over for a try, converted by O'Gara.
Munster: Tries: Horan, Murphy, Foley. Con: O'Gara. Pen: O'Gara
Munster: Lawlor, Carney, Murphy, Mafi, Horgan, O'Gara, O'Leary, Horan, Sheahan, Hayes, O'Callaghan, O'Driscoll, D. Ryan, O'Sullivan, Foley
Replacements: Pucciariello for Horan (66), Wyatt for O'Driscoll (71)
Not Used: Fogarty, Coughlan, O'Meara, Manning, Kelly
Scarlets: B. Davies, Daniel, Watkins, G. Evans, M. Jones, C. Thomas, L. Davies, John, Owen, Dunlea, Afeaki, A. Jones, D. Jones, Bater, N. Thomas
Replacements: Mackey for G. Evans (69), G. Evans for M. Jones (52), J. Davies for Dunlea (15)
Not Used: George, Cooper, G. Thomas, Stuart-Smith