The design of an electric urban car's chassis for the "Shell Eco Marathon" competition takes into account the usage and the type of the vehicle. The most critical factors of designing the new chassis are: the reduction of the weight, improvement of strength and stiffness and reduction of material and manufacturing cost. Towards this direction, a new design approach for a lightweight carbon-fiber reinforced epoxy (CFRE) monocoque chassis, is proposed, which conforms to structural, ergonomic and aesthetic requirements. For the development of this innovative approach, the parametric design method was chosen, in order for the design to be modified easily. The chassis efficiency, in terms of high strength in low mass, was obtained by following appropriate design steps and rules which conform to the vehicle structural and dynamical constraints and by choosing the composite material CFRE. Additionally, a method that calculates the mechanical properties of the composite material CFRE is presented. Furthermore, a model has been created, which calculates automatically the total loads applied on the vehicle's chassis. Worst case stress scenario was chosen and the model's output was evaluated for the new chassis design.