Abstract Research on explaining task-level knowledge management in achieving capital facility project success is limited. The purpose of this paper was two-fold. The first objective of this study was to validate a model for assessing the relationships between task-level knowledge management and project success. The second objective was to evaluate the moderating role of project characteristics in the relationship between task-level knowledge management and project success. This paper empirically investigated a sample of capital facility projects in the construction industry. The structural equation modeling (SEM) approach was used to validate the research model. These results suggested that knowledge management used in certain project tasks contributes to project success. On the other hand, the findings indicated that the relationship between task-level knowledge management and project success depends on team size, owner regulation, project environmental uncertainty, complexity, and time availability. Specifically, the results suggested that large project teams are more likely to achieve project success when they experience high levels of knowledge management than small project teams. Private projects are more likely to achieve project success when they experience high levels of knowledge management than public projects. It was also clear that projects under high and medium uncertainty may achieve higher levels of project success when they experience high levels of knowledge management than those under low uncertainty. In addition, projects with high and medium complexity were more likely to be successful when they experience a high level of knowledge management than projects with low complexity. Finally, the results also suggested that projects with an unrealistic schedule were more likely to be successful when they experienced a high level of knowledge management than projects with a realistic schedule.