This thesis will focus on the relationship between collaborations and the innovation of the circular construction industry. The reason for choosing to investigate this topic is because the construction industry is one of Europe's largest waste producers and energy consumers. Therefore, it can also make a big impact when the circular economy is implemented as efficiently as possible. According to het Planburea voor leefomgeving (2019), there is very little innovation in the circular economy, which does not favour the efficiency of the circular economy. On the other hand, the literature states that collaborations will be beneficial for implementing circularity in the construction industry. However, companies in other sectors that mainly work in-house (no collaborations) are frontrunners in the innovation of the circular economy. An example of this in the car industry is Tesla. They are a frontrunner in terms of electric cars and do 80% of the process internal (Benam, 2020). Out of this emerges the main question of this thesis. What is the relationship between collaboration and innovation in the circular construction sector? To support the main question, the four sub-questions will be answered first: RQ1: What kind of innovations are there in the circular construction sector? RQ2: What are the different elements of collaboration in the circular construction sector? RQ3: What are the factors that drive and prevent collaborations in the innovation of the circular construction sector? RQ4: Who are the stakeholders with whom collaboration should be established to facilitate innovation in the circular construction sector? The research method that will be used for this research is an exploratory study and the data collection will be done with the help of five case studies.