Problem statement - The global community is facing scarcity of finite materials and environmental pollution. In response to these mounting issues, the government of the Netherlands plans to transition to a circular economy (CE) by 2050. The shift towards a CE affects the built environment. Currently, the global building industry is responsible for 40% of material consumption and one-third of energy consumption. In essence, there are CE developments happening in the Public Real Estate (PRE) and barriers are known in the existing building stocks. However, insufficient research has been conducted on what the barriers could be for the existing PRE in regards to the CE transition. Barriers can hinder further CE development and the CE transition in existing PRE. What these barriers exactly are, has yet to be mapped out for the existing PRE. Therefore, sufficient research is needed to fill this gap. Hence, the following research question is then formulated for this research: “What are the current barriers to the circular economy transition for existing public real estate?”. Sub questions have been formulated in order to answer the main research question: 1. “How is the CE ambition integrated into CGREA’s existing PRE projects?” 2. “How are CE strategies implemented in existing PRE?” 3. “What challenges arise when implementing CE strategies in existing PRE?”. 4. “How are these challenges currently managed in order to realise the CE goal?”. This study explores three cases of the Central Government Real Estate Agencies (CGREA) existing PRE. The results will be used to identify and assess the current barriers for the existing PRE regarding the transition to a CE. Objectives - The aim of this study is to provide an overview of the current barriers to transitioning to a CE for the CGREA’s existing PRE. Moreover, the current CE activities around existing PRE will be analysed, and the facts and barriers for the CGREA will be established. Research method - The methodology of this study is divided into theoretical research, empirical research and synthesis. The research methods of this study consists of a review of previous scientific literature studies on the subject of CE in existing PRE, three case studies and interviews regarding the three cases, and an expert panel to assess, validate and improve the results. Discussion - In essence, this study contributes a more nuanced view on the subject of CE transition in the built environment focused on the existing PRE. The theoretical research indicated that the CE transition in existing PRE was neglected. Yet, empirical research indicated that the CE transition in existing PRE projects is being realised. Moreover, this study has found that, even if the CE ambition is integrated into the later stages of a project, it is still difficult to realise this ambition with the current economy we live in. The analysed cases have indicated the challenges that are an obstruction for further transition to the CE. These challenges are identified and validated as barriers. Conclusion - In this study twelve barriers were identified and assessed that are currently a barrier for further CE transitioning in existing PRE. These barriers are: that there is (1) No CE ambition in the project scope, (2) unknown resource availability, (3)No assessment framework, (4) Inexperience of the contractor with the CE, (5) Cost and time driven projects, (6) No separate budget for CE strategies, (7) Finding CE installations, (8) Unknown quality of building materials, (9) current regulations, (10) No CE award criteria, (11) Users satisfaction, and (12) Definitive design without CE strategies.