Dioxazolones and phosphines have been used to access N-acyl iminophosphoranes in copper(I) catalysis under simple thermal conditions. The synthetic utility of this protocol is demonstrated by a broad range of substrates with an excellent atom-economy. The optimization process showed that copper demonstrated as catalytic amount toward the targeted transformation. Functionalization studies of N-acyl iminophosphoranes were also conducted. Our reaction protocol is compatible with an example of a bioactive motif-containing N-acyl iminophosphorane analogue. © 2023 Wiley-VCH GmbH.