Organophosphorus aza-heterocycles are widely found in the framework of numerous bioactive molecules, functional materials, and commercially available drugs. We report herein a photoredox-catalyzed radical addition cascade annulation sequence of acyclic phosphinimides with a variety of organohalides under mild and external oxidant-free reaction conditions. A wide range of functionalized phosphinimides bearing a quaternary carbon center could be efficiently and selectively produced by employing diverse radical precursors, including sulfonyl, perfluoroalkyl, trichloromethyl, and carbonyl halides, under mild reaction conditions.