This paper addresses a multi-objective sustainable supply chain optimization problem integrating transportation and cross-docking operations under strict temporal and environmental constraints. A mixed-integer linear programming (MILP) formulation is proposed to jointly optimize vehicle routing, fleet activation, handling operations, and time-window compliance while explicitly accounting for CO₂ emission costs. The model captures multi-day planning and enforces synchronization between supplier, cross-dock, and customer flows. An exact solution approach based on IBM ILOG CPLEX is implemented using the DOcplex library to validate the structural feasibility of the model and to generate optimal benchmark solutions. Computational experiments on small-scale instances demonstrate the robustness of the proposed formulation, highlight the dominance of fixed vehicle costs in cross-docking systems, and confirm the effectiveness of the integrated environmental modeling. While exact solutions are obtained efficiently for modest instance sizes, the results also reveal computational limitations as problem size increases, thereby motivating the use of metaheuristic approaches for large-scale applications......... Keywords:.......Sustainable supply chain; Cross-docking; Exact optimization; Mixed-integer linear programming; Transportation.