Method and set of surgical instruments for fitting a shoulder prosthesis, and the shoulder prosthesis. The proposed method seeks to interpose a bone graft between the previously prepared glenoid surface (G) of a scapula (S) of a patient's shoulder and the face of a glenoid prosthetic component opposite the articular surface. The set of instruments permit the bone graft to be taken from the upper epiphysis of the humerus (H), either in situ or ex vivo.