High-powered ultrasonic spot welding of metals is receiving growing interest as a prominent candidate to replace resistance spot welding, particularly of aluminum alloys, due to features such as solid-state welding, low energy consumption, short welding time, and long tool life. In this method, high-frequency ultrasonic vibrations are applied to overlapping components held under normal static force. A relative motion of very short amplitude is generated between the two surfaces, which breaks the oxide films and brings fresh metal surfaces into contact, whereupon a metallurgical bond is developed. The current study was conducted to investigate the characteristics of ultrasonic spot welding of AA6061-T6 aluminum alloy. Tensile lap shear tests were performed to evaluate the strength of joints produced with different welding parameters. Furthermore, the influence of weld energy on joint attributes was characterized through microstructure examination and micro-hardness measurement. It was possible to optimize the welding parameters to obtain joints of high strength. The results revealed that the higher the weld energy, on the one hand, promoted joint strength and on the other hand, expanded the softening area in the welded components.