This paper presents the volumetric and Marshall Stability characteristics of irradiated waste polyethylene terephthalate fiber-reinforced asphalt mix utilizing the analysis of variance. Exposing polymers to gamma radiation boosts its mechanical and thermal properties which have a direct impact on improving its strength. The influences of irradiated fiber and binder contents on the volumetric and strength properties have been identified via response surface methods (RSM). The RSM was used to determine the optimized contents of irradiated fiber and binder through central composite design (CCD). The results indicate that the interactions between the two independent variables are both influential. The high values of the coefficient of determination (R2) show a good agreement between the actual and predicted values. The numerical optimization elucidates that the optimal irradiated fiber and binder contents were 0.53 and 5.25 respectively. The absolute percent errors between the actual and predicted values were observed to be less than 7 for all the responses. © 2020 THE AUTHORS