© 2020 American Society of Civil Engineers.Although complexity and risk are inherent characteristics of megaconstruction projects, existing project management approaches fail to incorporate complexity-based thinking into risk management. Complexity is usually considered as the source of risk events, along with uncertainty. However, prevailing risk management practices are oriented toward only handling the uncertainty. The lack of integration between the complexity and other risk-related concepts leads to unrealistic project risk assessments and the formulation of imperfect management strategies. The aim of this research is to explore the relationship between complexity and risk in detail and propose an integrated risk assessment approach. For this purpose, a mixed-methods research approach was adopted to collect data via semistructured interviews and survey questions. Data obtained from 11 megaconstruction projects carried out by Turkish contractors were analyzed in two ways. Quantitative findings served to verify the relationship between complexity and risk in numerical terms, whereas qualitative findings were utilized to develop a framework that explains the nature of this relationship. The conceptual framework represents the links between complexity and risk in megaconstruction projects, together with uncertainty and management strategies. The existence of causal relations between these concepts may constitute a significant challenge during the risk assessment. Therefore, an integrated risk assessment process (IRAP) was proposed so that megaproject practitioners could develop better risk management plans. The findings of this research were based on megaconstruction projects, but they may also apply to other types of projects.