The aim of this study is to investigate the effect on shear load and microstructure of AA6061-O aluminum sheets joined using friction stir spot welding (FSSW) by different welding parameters and post-weld heat-treatments (PWHT) T4 and T6.Taguchi method was used as an experimental statistical model to determine the optimum FSSW parameters. Taguchi's L27 orthogonal array was used to arrange the experiments. Three tool rotational speeds of 1200, 1500 and 1800 rpm and three dwell times of 6, 8 and 10 sec were used to conduct the welding. After FSSW, the AA6061 joints were subjected to T4 and T6 heat treatments. The findings showed that the grain size of stir zone (SZ) increased by either increasing rotational speed or increasing dwell time. Shear load significantly increased as dwell time increased. Shear load for the welded joints after heat treatment (T4) are greater than(T6), both of them are greater than O-condition.