A novel metal-free, efficient cascade reaction has been developed to construct 1,2,3-triazole-fused 1,4-diazepinone skeletons. Mechanism investigation indicated that sodium azide has not only served as a 1,3-dipoles synthon in [3 + 2] cycloaddition but also prompted C-N bond formation. Furthermore, the potential utility of this protocol was demonstrated by scale-up synthesis of 1,2,3-triazole-fused diazepinone derivatives and the derivatization of them.