Abstract This research work deals with the theoretical investigation of the coexistence of superconductivity and ferromagnetism in superconductor CeO (x = 0 1:0). By developing a model Hamiltonian for the system and using the Green's function formalism and equation of motion method, we have obtained expressions for superconducting transition temperature (T c ), magnetic order temperature (T m 1x F x BiS 2 ), superconducting order parameter ( ) and magnetic order parameter ( ). By employing the experimental and theoretical values of the parameters in the obtained expressions, phase diagrams of energy gap parameter versus transition temperature (superconducting transition temperature versus magnetic order parameter and magnetic order temperature versus magnetic order parameter) are plotted separately. By combining the phase diagrams of superconducting transition temperature versus magnetic order parameter and magnetic order temperature versus magnetic order parameter, we have demonstrated the possible coexistence of superconductivity and ferromagnetism in CeO 1x F x BiS superconductor. Our nding is in agreement with previous experimental ndings. 2 Key words: Superconductivity, ferromagnetism, coexistence, CeO , Green's function. 1x F x BiS 2