Herein, the roles of an Al/Fe2O3 energetic composites as a heat energy source and a bonding medium for interfacially bonding dissimilar Al/Cu metallic substrates are systematically investigated. Energetic material (EM)/solder material (SM) bilayer pellets are assembled and ignited between the interfacial Al/ Cu substrates for bonding. The upper EM layer comprising an Al microparticle (MP)/Al nanoparticle (NP)/ Fe2O3 NP composite serves as a heat source for melting the lower SM layer comprising SAC305 MP for strongly bonding the Cu substrate with the melted SM layer. The intermetallic compounds (AlxFey) formed during the aluminothermic reactions of the ignited EM layer play an important role as a bonding medium between the Al substrate and the melted EM layer. The dissimilar Al/Cu substrates are interfacially bonded using an EM layer with a fuel-to-oxidizer ratio of 1.97-4.44. The maximum mechanical strength of the bonded Al/Cu substrates increases with the increase in the fuel-to-oxidizer ratio owing to the supply of sufficient heat energy under fuel-rich conditions. The EM layer acts as an effective heat energy source and mechanical bonding medium. The proposed interfacial bonding technique is simple, easy, and versatile for welding and joining dissimilar metallic substrates for industrial applications.