Many firms are pursuing ISO 9000 certification—an international standard for quality management and quality assurance—as a means of enhancing competitiveness through quality innovation. However, despite widespread corporate interest, considerable confusion and controversy exist regarding the role and value of certification, as there are significant differences in its effects even among certified firms. This study considers certification type as a major factor causing post-certification performance differences and analyzes how certification performance varies according to these types. Furthermore, recognizing that certification performance depends not on certification acquisition itself but on continuously creating and building a TQM environment both during and after the acquisition process, the interaction effects between certification type and quality management activities were analyzed. According to the research results, organizational performance improvement through ISO 9000 certification acquisition is closely related to certification motivation, and the degree to which quality management activities are performed differs according to this certification motivation. Specifically, stronger certification motivation was associated with greater certification performance and more active quality management activities compared to weaker certification motivation. Additionally, quality management activities were found to exert a moderating effect, showing that certification performance can be further enhanced when certification motivation is proactive and quality management activities are actively performed. However, the certification standard was found to be unrelated to performance and the degree of quality management activity execution, indicating that it is not a major factor causing performance differences.