The C-H addition of sulfides to alkenes is an atom-efficient route for the functionalization and modification of sulfide compounds through C-C bond formation, but this transformation is highly challenging. We report here the regioselective alpha-C(sp(3))-H addition of a wide range of methyl sulfides to a variety of olefins and dienes by a half-sandwich scandium catalyst. This protocol provides a unique route for the synthesis of diverse sulfide derivatives through C-C bond formation at a sulfur-adjacent carbon atom in a 100% atom efficient fashion.