This Article describes the development of a stable Ni-IV complex that mediates C(sp(2)) - H trifluoromethylation reactions. This reactivity is first demonstrated stoichiometrically and then successfully translated to a Ni-IV-catalyzed C-H trifluoromethylation of electron-rich arene and heteroarene substrates. Both experimental and computational mechanistic studies support a radical chain pathway involving Ni-IV, Ni-III, and Ni-II intermediates.