Stability performance of cylindrical shells and providing a potential method to enhance the buckling stability of these structures are major concerns for designers. Carbon Fiber Reinforced Polymer (CFRP) composites are promising materials for application in the design and retrofit of such thin-walled structures. On this basis, this paper presents a comprehensive numerical study on the buckling behavior of CFRP-strengthened cylindrical shells under uniform external pressure and evaluates the effects of different parameters in the strengthening process. Numerous CFRP-strengthened cylindrical shells with distinct reinforcement layouts in three groups of models having different slenderness ratios are investigated through nonlinear stability analyses using the ABAQUS finite element package. The application of all considered reinforcement layouts for strengthening purposes is found to be effective in improving the buckling stability of cylindrical shells. It is demonstrated that the circumferential reinforcement of the middle region of the shell using CFRP strips with [0°] fiber angle (in the hoop direction), in particular, is the most effective approach for improving the buckling performance of the CFRP-strengthened cylindrical shells under uniform external pressure.