In this research work an attempt has been made to develop an empirical relationship between FSW variables and the mechanical properties (tensile strength, yield strength, percentage elongation, micro hardness and impact toughness) of friction stir welded aluminium alloy 6082-T651 joints. Central composite design matrix was used to prescribe the required number of experimental conditions. A four-factors-five-level central composite design was used to determine the optimal factors of friction stir welding process for aluminium alloy. The central composite design (CCD) with a quadratic model was employed. Four independent variables namely - tool rotational speed (N), welding speed (S), axial force (F) and pin diameter (P) was selected. The mathematical relationships were developed from the data generated. The developed mathematical relationships were useful for prediction of tensile strength, yield strength, percentage elongation, micro hardness and impact toughness in friction stir welded AA6082 aluminium alloy joints at 95% confidence level. The micrographs showing the microstructure of base material and all the welded joints are presented.