We report a combined experimental and mechanistic study on the Buchwald-Hartwig amination and C-S/S-H metathesis of aryl sulfides by selective activation of C-S bonds mediated by well-defined, air- and moisture-stable Pd(II)-NHC precatalysts, [Pd(NHC)(μ-Cl)Cl]2. This class of Pd(II)-NHC precatalysts displays excellent activity in the cross coupling of aryl sulfides. Most crucially, we unravel the unified mechanism for activation of C-S bonds in the C-N cross-coupling and C-S metathesis manifolds, where the inert C-S bond serves as a precursor to valuable amine or thioether products.