The goal of this research is to provide insights into the relationships between complexities and risks to be used in risk analysis and management of complex construction projects. In preparation of the exploratory survey, a literature study is performed. After that, the CBRAT (Complexity Based Risk Assessment Technique) is designed to capture the cause-effect mechanisms between complexity elements and risk-factors. The CBRAT consist of the TOE (Technical-Organisational-External) framework, a RBS (Risk Breakdown Structure) and a risk-influence diagram. After that, the applicability of the CBRAT was tested on the Frankfurt Airport Terminal 3 project. In general, it can be concluded that it is of importance to process the complexities in construction projects more consistently during the implementation of risk management.