Steel jacketing has widely been used for seismic retrofit to improve the ductility of reinforced concrete columns. This paper proposed a tetra-linear hysteresis model of steel jacketed columns to analyze the response of retrofitted structures. The model is constructed based on the results of cyclic loading tests. The authors evaluate the strength of columns ignoring the steel jacket and the ductility considering the stiffness of cover concrete, mortar filler and the steel jacket which resist buckling of longitudinal reinforcing bars. The proposed model simulates the deformation capacity of steel jacketed columns appropriately.