Purpose This study is based on previous studies related to the function and operating system of the project management system for efficient project management. The purpose of the study is, first, to find out how the project performance is affected by the utilization of the project management system and the involvement of the PMO. Second, the mediating effect of implementing integrated management between the project management system and project performance is to be demonstrated. Design/methodology/approach Based on previous studies related to project management, this study designed a research model by integrating functional factors derived from project management system design studies, integrated management factors, and factors derived from PMO function studies. Findings As a result of the empirical analysis, this study first confirmed that high utilization of the project management system and high involvement of the PMO are factors that affect project performance. In addition, it was confirmed that the establishment of the system and the introduction of PMO do not guarantee project performance. Second, it was confirmed that the execution of integrated management has a mediating effect between the system and the project performance, and that the high utilization of the system has a positive effect on the mediating effect.