Nowadays reducing weight of products especially for the products that cause environmental pollution such as vehicles is not only an option, but also an obligation. In the current work, design of a chassis frame of a commercial vehicle is performed in order to reduce the weight. The work is dived into two parts. topological optimization of frame is done for some target functions. For investigating load paths as well as overall shape of the frame, a pseudo density with values, between 0 and 1 is considered for each element as the design variable. By relating stiffness of each element to this pseudo density and defining the minimum compliance as the objective function and the maximum volume fraction as the constraint, the elements which have less structural role are omitted during the optimization process to minimize mass of the structure. Pareto optimality concept and weighted sum methodis used toMinimize compliance under multiple loading cases. The process is begun by defining design space which is the allowable space that chassis frame can be placed in. Then the design space is meshed and suspension system which is modeled as a mechanism is attached to the frame by rigid elements. After that loads and boundary conditions are applied and topological optimization is performed for different combination of weights. After plotting compliance of symmetric bending against asymmetric bending for each weight combination, optimal weights are determined that are related to points having minimum distance to ideal points. An ideal point is a point in which each function has its minimum value, but it is not an accessible point and is just for comparing other points with it. After investigating the results of topological optimization, three different concepts are presented for the chassis frame. The beam finite element model of each concept is developed.Dimensional optimization is done for each of three concepts to reduce the weight under maximum allowable stress constraint. After comparing the concepts in different aspects, the best one is chosen. In the next phase, joints of components and mounts of suspension systems are designed using topological optimization methods. Shell finite element model of the whole chassis frame is prepared and analyzed. The results are compared with the beam model and they show proper compatibility between results of two models. Finally, the weak points of the chassis are identified and appropriate solutions for covering them are presented. The final design of chassis frame has proper structural properties even though it has low weight. keywords: Topology optimization, Pareto optimality, Chassis frame, Lightweight structure, Design