In a context of project-based organization reinforcement, the question of knowledge management has become an issue for companies as well as for research in management. The point for the companies is to jointly manage the knowledge development and the development of innovative products and services through projects. The literature recognizes the need for a link between knowledge management and project-based organization, but contributions are nonetheless limited when it comes to distinguish the various levers of action that could be triggered to manage knowledge together with projects. The purpose of this paper is to highlight the different levers of this joint management. Our research is based on a qualitative approach, centered on a multiple case study, undertaken within four project-oriented companies operating in different sectors: IBM, Hewlett-Packard, Arkopharma, and Temex. The analysis of the four cases, in the light of the existing literature, enables us to identify and discuss eight levers of action ensuring the link between knowledge management and project-based organization: formalization of project management, post-project analysis, project documentation and its computer storage, professional communities of practice, physical proximity of the actors, staff inter-project meetings, occupational projects, and research and development upstream. The paper is original because it investigates the framework of levers of action to improve the understanding of knowledge management in project-based organizations.