This study tried to find out the effect of change management on the ERP performance in small and medium size companies. Communication, BPR management, education and training were selected as independent variables which might bring an effect on ERP performances which were classified as quality and quantity one. Structure equation model was built and analyzed with AMOS 5.0 version from data gathered through 127 companies which already implemented ERP systems. The result of this study shows that all the three independent variables give positive impacts on two dependent variables, which means change management is critical when small and medium size companies want to implement ERP systems.