Enterprise Resource Planning (ERP) projects have often been found to be costly, complex, and risky to implement in enterprises. Therefore, understanding ERP implementation risks can help reduce the failure of ERP projects. The aim of this study was to explore two questions: (1) Do the six risk dimensions (planning & control, requirement, organization environment, user, team, and project complex) have different impacts on ERP project implementation success? (2) Which critical risk factor among the six risk dimensions is the most important to be resolved for the achievement of ERP project implementation success? The research results not only revealed the six risk dimensions associated with ERP system implementation success, but also showed that the significant risk factors among the six risk dimensions which managers must mitigate or eliminate are "Unclear goals," "Lack of ERP fit to organizational process," "Lack of organizational change," "Users are not ready to use an ERP system to assist their work," "IT members' lack of specialized knowledge required by the ERP project," and "Difficult to integrate the ERP with other IT systems," which knowledge could be used to prepare an effective ERP project risk management plan to increase ERP implementation success.