Despite wide acceptance of ISO 9001, research shows mixed results about the performance benefits. Even though some studies show positive benefits of ISO 9001, lack of studies find that ISO 9001 leads to higher performance. As the ground reality was questioning this theory, this study was conducted to determine the critical factors affecting the operational performance in implementing quality management system (QMS) standard based on ISO 9001:2008 requirements in Port X. There were a total of 103 respondents participated in this study, who are the employees at Port X. The data obtained from the survey was analyzed using SPSS software. Based on the results obtained from the descriptive analysis, it was found that the order of level of importance of QMS critical success factors as perceived by the respondents was top management support (M = 4.26±0.33), quality process management (M = 4.19±0.36), continual improvement (M = 4.16±0.31), measurement, monitoring and control (M = 4.15±0.31), human resource management (M = 4.14±0.34), and customer focus (M = 3.94±0.34). It was also revealed that there was a high level of overall perception (M = 4.32±0.30) among the employees towards the company’s operational performance. From the correlation analysis, there were only two of critical factors were found to be significant predictor of operational performance: top management support and continual improvement. Both factors have significant moderate and positive correlation with operational performance. In addition, it was found that all critical factors could be used to predict 47.7% of operational performance. This significant finding obtained for both critical success factors serves as an evident that the appropriate practice of these two QMS critical success factors is significant and positive to the operational performance
