Conflicts, claims, and disputes cause cost and schedule overruns in construction projects. Previous research studies have considered contractual risks as one of the main factors affecting the performance of modular construction projects. In fact, modularization requires unique contractual agreements that foster the successful implementation of such construction method. This paper identifies the causes of disputes in modular construction projects. To this end, a multi-step interrelated research methodology was used. First, the authors collected and analyzed 15 actual national case studies reflecting disputes in modular construction projects. Second, social network analysis was conducted where frequency analysis and centrality measures were used to identify the top causes of disputes as well as understand the dispute causation network in modular construction projects. The results showed that the common causes of disputes in modular projects include: (1) delays in work progress, (2) lack of team spirit, and (3) lack of communication. The analysis of the dispute causation network identified the lack of collaborative environment and adequate communication among the project stakeholders as primary contractual risks in modular projects. Ultimately, this paper adds to the body of knowledge by helping practitioners in better understanding the contractual risks that should be addressed to minimize disputes in modular construction projects.