The construction industry imposes significant pressure on the natural environment, making it essential to transition to the circular economy. A step towards this goal is the adaptive reuse of existing buildings, more specifically, heritage buildings. Adaptive reuse of heritage is a difficult procedure that seeks to maintain the qualities of historic structures while modifying them for usage in the present and the future. The aim of this research is to identify what circular economy strategies are implemented in de adaptive reuse of heritage buildings, find out what barriers still exist, and how these can potentially be mitigated. This in order to help the transition towards the circular economy. To achieve this, literature review will provide a better understanding of the terms circularity and adaptive reuse within the context of the built environment and heritage, the literature study will also offer the potential barriers for circular heritage renovation. Case studies will explore what strategies are already implemented in adaptive reuse of heritage buildings, and barriers are experienced in the process. Finally a focus group discussion will be conducted in order to find out how these practical barriers can be mitigated in order to move towards the circular economy. The findings reveal that there is a gap between the strategies implemented in projects and the comprehensive understanding of circular economy . The majority of implemented strategies are related to sustainability, such as reusing and using circular building materials. Barriers to implementation include ambiguities, financial constraints, lack of experience, routine practices, rules and certification, as well as a lack of urgency and social acceptance. To address these challenges, the Circular Economy Strategies for Adaptive Reuse (CESAR) model is developed as a planning and assessment tool. Furthermore, the study provides advice for stakeholders involved in adaptive reuse projects, emphasizing the importance of collaboration, early involvement of the contractor, and integration of circular economy requirements.