A photoinduced three-component radical addition-aminalization cascade was accomplished, enabling rapid assembly of a wide range of densely functionalized γ-lactams. Key to this transformation is the electron-donor-acceptor (EDA) generation of enamine and in situ trapping of an iminium intermediate with bromodifluoroacetamide. This rationally designed protocol fully takes advantage of the polarity crossover (enamine-iminium) in the process, providing the modular assembly of previously inaccessible scaffolds. The reaction proceeds under mild reaction conditions with excellent regio- and diastereoselectivity, which is amenable to structurally varied substrates and pharmaceuticals.