This Article describes the development of a stable NiIV complex that mediates C(sp2)–H trifluoromethylation reactions. This reactivity is first demonstrated stoichiometrically and then successfully translated to a NiIV-catalyzed C–H trifluoromethylation of electron-rich arene and heteroarene substrates. Both experimental and computational mechanistic studies support a radical chain pathway involving NiIV, NiIII, and NiII intermediates.