In the present investigation, friction stir spot welding (FSSW) on AA6061-T4 aluminium alloy plates was performed. The influences of the tool rotational speed, dwell time, plunge depth and plunge rate on tensile-shear load of welds were evaluated. The process parameters were optimized by Taguchi technique based on Taguchi’s L9 orthogonal array. The optimum FSSW process parameters were predicted, and their percentage of contribution was estimated by applying the signal-to-noise ratio and analysis of variance. The experimental results showed that the optimal levels of the rotational speed, plunge depth, plunge rate and dwell time were found to be 2000 rpm, 0.9 mm,10 mm/min and 8 seconds, respectively. The analysis of variance (ANOVA) results showed that the plunge depth is the most influential FSSW process parameter on the tensile-shear load with a percentage of contribution of 55 % of the overall response. The rotational speed, plunge rate and dwell time FSSW process parameters showed percentage of contribution of 17%, 5% and 23%, respectively, of the overall response.