Supplier selection is an important decision in the management of a supply chain. Recent emphasis on sustainability in supply chain management has made this selection more complex. In  this  paper  the  sustainable  supplier  selection  criteria  and  sub-criteria  are  determined. Based on those criteria and sub-criteria a methodology is proposed in supplier evaluation and order allocation. Gray relational analysis is used to sustainability supplier evaluation and a bilinear goal programming model is developed for supplier selection and order allocation. Bilinearity in the model is handled with a modified Benders decomposition method and numerical results shows the efficiency of the proposed model. Implications of the model and future research directions are presented as the paper conclusion.