Confinement of reinforced concrete (RC) columns through external bonding (EB) of fibre-reinforced polymer (FRP) composite becomes less effective in non-circular sections. The effectiveness of FRP confinement reduces with an increase in the size of the cross-section. Hence, it is essential to develop an effective FRP strengthening technique for large-sized square columns. Hybrid FRP strengthening combines the advantage of both near-surface mounting (NSM) and EB strengthening procedures for enhancing the overall performance of RC members under different load combinations. Sixteen square RC columns of various size ratios 1.0 and 1.5 were cast, strengthened and tested to understand the efficacy of the hybrid FRP technique. In addition to the tests, detailed nonlinear finite element (FE) models were developed and validated with the test results and data from the literature. Results show that the efficiency of EB and Hybrid FRP strengthening decreased with the increase in sectional ratio of square columns. Hybrid FRP strengthening improved strength and ductility for all size ratios compared to EB or NSM FRP strengthening alone. Using validated FE models, a parametric study was also conducted to understand the effect of EB and NSM reinforcement ratio and column size on the efficiency of Hybrid FRP strengthening.