One of the key issues in Enterprise Resource Planning implementation is what critical success factors should be managed to increase the chances of a successful implementation. The purpose of this study is to examine critical factors that affect successful implementation of Enterprise Resource Planning in Commercial Bank of Ethiopia. To achieve this objective quantitative research approach and explanatory research design were used to examine the effect of critical factors that affect successful implementation of Enterprise Resource planning in the case company. Purposive/judgemental sampling was used to select the appropriate samples of the study and to collect data for the study questionnaires were distributed to 200 employees in Commercial Bank of Ethiopia at head office. Correlation and regression analysis were conducted based on 176 responses from 200questionnaires. Findings of the study showed that all the independent variables are top management support, project management, user training, business plan and vision, technological infrastructure, change management and cooperation and communication were positive and significant correlation with dependent variable which is successful implementation of ERP. In the model summery the test result showed that, the value of R and R2 was statistically significant. And the multiple regression analysis confirmed that from the 7 independent variables 6 variables have statistically significant relationship to predict ERP implementation success. Only one variable (cooperation and communication) is not statistically significant relationship to predict ERP implementation success. Hence, the researcher recommended that CBE has to give emphasis for critical factors in order to maintain the successful implementation of ERP and reduce the possibility of ERP implementation failure.