Friction stir spot welding (FSSW), a solid state joining process and a linear variant of Friction stir welding, has been used in industrial sectors for joining dissimilar materials like aluminium and copper alloys having different mechanical and metallurgical characteristics. In this paper, experimental evaluation of aluminium (Al) commercial alloy (Al 5083 – H111) and oxygen free copper (C10100) joints, using this technique, has been attempted, by varying the important process parameters such as tool rotational speed (RS) in rpm, plunging depth (PD) in mm and duration of dwell (DT) in seconds. Microstructural study using scanning electron microscopy was conducted to evaluate the mixing of the base materials in the weld interface. The grain structure and morphological changes were studied to predict the effect of stir. The effect of process parameters on the tensile shear failure load of joints were observed. Energy-dispersive X-ray spectroscopy was used for evaluating intermetallic compounds at joint interface. The presence of intermetallic compound AlCu was detected at the joint interface,  formed during FSSW process at parameters RS-1250 rpm, DT-12 sec, PD-2.1 mm. The interface regions were found to be a finely fused combination of aluminium and copper in most of the regions and chaotic in certain places.