External confinement of reinforced concrete columns using fiber-reinforced polymer (FRP) sheets can significantly enhance their seismic behavior. This research presents a numerical investigation to evaluate the seismic performance of RC rectangular columns with limited cross-sections' aspect ratios (1, 1.5, and 2) strengthened with a fully wrapped CFRP jacket under constant axial and pushover lateral loads. Therefore, a three-dimensional finite element model was implemented via ABAQUS software, which has been adopted in this study, where the proposed model showed a reliable agreement with the previous experimental work. The studied parameters are: longitudinal steel reinforcement ratio, CFRP confinement ratio, and axial load/capacity ratio for each cross-section aspect ratio. The obtained numerical results have proved that the external wrapping of RC rectangular columns with CFRP sheets has effectively increased drift capacity ratios for cross-sections aspect ratios 1, 1.5, and 2. Moreover, the strengthening of RC rectangular columns using external CFRP wrapping increases the nominal shear and flexural strengths of the strengthened columns. Also, the effect of increasing the longitudinal steel reinforcement ratio can significantly decrease the ultimate lateral displacement and drift capacity ratios. Besides, with the increase of the axial load/capacity ratios, the drift capacity ratios significantly decrease for the strengthened RC rectangular columns.