This paper seeks to propose a theoretical model capable of guiding investigations dedicated to the contributions of Project Management Offices (PMO) to the organizational strategy in Project-based businesses (PBB). A systematic review of the literature was conducted in the databases Web of Science and Scopus in order to identify the papers that went over the topic.The gathered sample was made of 19 articles, which were explored through the content analysis technique based on Saldaña´s coding cycles (2016). The results identified that PMO contribute to strategies through actions aimed at project integrity, monitoring activities, integrating and communicating between projects and people, standardizing instruments and methods, aligning strategic objectives, and portfolio management. It is understood that by developing those activities, the PMO are supporting the strategies, linking them to the projects, and creating a favorable environment for their realization. This study contributes to the literature by generating an understanding of how to integrate projects into organizational strategies in the context of PBB and offer a more specific view of how PMO support the process of implementation of strategies in PBB. Its originality is based on the role of the PMO in the context of PBB.