A visible-light-mediated cycloaddition of azobenzenes and nonstabilized azomethineylides has been developed to access 1,2,4-triazolidines. With readily available organic dye rose bengal as a photocatalyst and alkyl tertiary amines as precursors for azomethineylides, the reaction proceeded smoothly under visible light irradiation at room temperature, affording various 4-alkyl-1,2-diaryl-1,2,4-triazolidines