Purpose: The study aims at investigating the determinants of successful project management practices on performance of roads projects at Kenya National Highways Authority. This study was limited to four variables, which include project monitoring, management support, Project team, and Project funding.Methodology: The study employed a descriptive research design. The target population included the top project management team of KeNHA, Monitoring Officers of KeNHA, Project Engineers (PEs), financial officers and auditors, Consultants and Contractors in the entire structure of KeNHA totaling to 174. The study employed stratified random sampling technique to acquire a sample size of 87. The study collected both quantitative and qualitative data through the use of a organized survey of questionnaire. Data was presented in the form of frequency distribution tables, graphs and pie charts that facilitates description and explanation of the study findings. Results: The study findings revealed that project monitoring, management support, Project team competency and Project funding influence performance of roads projects at KeNHA. The results of findings indicates that a unit increase in project monitoring, management support  Project team competency and Project funding leads to 0.873, 0.581, 0.713 and 0.289 increase in performance of roads projects at KeNHA respectively. The study concluded that Project Funds greatly influence road Project Completion. Recommendations: The study recommends that management should provide the necessary provision to the practical and operating workers in the development of road project operations for real and practical success of objectives. Highly qualified and experienced management support with a relevant experience and technical skills should be hired to implement road projects. This will enable the Kenya government get value for their money, achieve on-time projects completion and save huge costs.