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.