Buckling of the stiffened composite cylinder is a very complex phenomenon that involves complex interactions between the skin and the stiffeners. Depending on different parameters, different buckling failure modes and failure loads are observed in stiffened composite cylinders. A 3-D finite elements model was built using ANSYS, which takes into consideration the exact geometric configuration and the orthotropic properties of the stiffeners and the shell. The effects of several parameters such as fiber orientation, shell thickness, and elastic material properties were carried out and general conclusions were drawn regarding the optimum configurations of the different parameters of the ring-stringer stiffened composite cylinder. The study corroborated that global buckling failure mode should be the design criteria for the stiffened composite cylinder.