Cu/Al bimetals were fabricated by diffusion welding (DFW) at welding temperatures ranging between 683 and 803 K, welding time between 20 and 80 min, and a welding pressure of 15 MPa. The scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) results of the Cu/Al interface showed that the width of interface layer gradually increased with increasing welding temperature and prolonged welding time. Following welding at 803 K for 80 min, intermetallic compounds (IMCs) of Al4Cu9, Al3Cu4, AlCu, and Al2Cu occurred at the Cu/Al interface from the copper side to the aluminum side. The IMCs occurred in the sequence of Al2Cu, AlCu, Al3Cu4, and Al4Cu9 . Shear test of Cu/Al bimetal showed brittle facture, and the interfacial strength increased with lower amount of IMCs. A maximum shear strength of the Cu/Al bimetal of 63.8 MPa was obtained following DFW at a welding temperature of 723 K for 20 min.