The effect of optimum concentration of TiO2, Al2O3 and ZrO2 nanoparticles on lap shear joint strength and joint toughness (area under the engineering stress-strain curve) of epoxy nanocomposite adhesives has been studied. Two types of processing techniques such as conventional ultrasonic vibration (CUV) and ultrasonic dual mixing (UDM) were used to disperse nanoparticles in epoxy adhesive in order to develop epoxy nanocomposites. Aluminium-adhesive-aluminium joints were tested, and their fracture surfaces were characterized using FESEM to understand the role of toughening mechanisms on the performance of the joints. The outcome of the present study exhibited the importance of oxide nanoparticles in controlling the strength of epoxy adhesive based metal joints having significant applications in automobile and aerospace industry.