Complex construction Projects represent time-consuming projects that have complexity in structural systems, building control systems or in their architectural design. In general, the objective of risk management is to predict, reduce and avoid the risks and their consequences. The primary objective of this research is to undergo a cause-and-effect analysis of the key risks that face complex construction projects, thus enhancing their project delivery success. The methodology used is an integrative review of the existing literature on the key concepts including risk management of complex construction projects .In addition, qualitative analysis of the case study of the Grand Egyptian Museum, as one of the pioneering complex projects, has been performed to analyze key causes of risk in this type of projects. The study covers the period from 2014 to 2016, as the project is still in progress. Finally, a survey targeting stakeholders involved in the construction and management of complex construction projects was conducted. The study findings shed light on the key causes and effects of risks affecting the success of complex projects and their effect on different project constraints. The study results showed that root causes of risks are mainly related to managerial complexities in the project. These complexities are namely: lack of proper management and uncertainties in management goals and methods. Technical complexities, however, have the most severe impact on the risks affecting complex constructions. The top identified risk was found to be improper planning, followed by legislative risk, and scope changes. These results make it clear that managerial complexities are of the same importance as technical complexities. Thus, this study underscores the role played by efficient management in managing risks and in enhancing the success of complex construction projects delivery process