Nowadays, knowledge management becomes a key challenge in modern organizations, especially project-based organizations. As a central unit in a project-based organization, a project management office (PMO) plays a pivotal role in projects’ success and organizational performance. Consequently, PMOs need to build an effective knowledge management system that renders them more efficiency and effectively. This paper aims at proposing a conceptual framework for promoting knowledge management in PMOs. The paper begins with a review of the literature on knowledge management and activities in PMOs to provide a clear understanding of knowledge management in PMOs. Then the paper suggests an overall architecture of the knowledge infrastructure for PMOs. Finally, a framework is proposed for building an effective knowledge management system for PMOs based on the perspective of knowledge components that could help PMOs create more business value by classifying information formally and enabling its transformation into valuable knowledge assets.