Fatal accident rates in the U.S. construction industry trail behind other developed countries. Previous research investigated accident causation, but no studies focused on the relationship among root causes for construction fatalities. This research aims to analyze the interaction between fatal accident root causes and their relationship to commonly quoted direct causes using social network analysis (SNA). SNA is an analytical technique evolving from graph theory used in multiple fields including social sciences, natural sciences, construction management, and safety. To achieve this goal, a three-step methodology is devised. First, data about accident causation was extracted from 100 case files. Second, an SNA model was developed and performed at an aggregate level analyzing the fatalities causation network as a whole, as well as at a disaggregate level to pinpoint root causes of the fatal four accident direct causes. Third, the results of the model are interpreted and validated to draw conclusions about accident causation and underlying factors leading to fatalities. The model successfully identified the key root causes of construction fatalities and the interrelationships among them. For example, it indicated that lack of job-specific training is the most central cause of "struck by," and "caught in between" accidents. It also indicated that the absence of fall arrest systems, lack of jobsite training, and lack of personal protective equipment are the most interrelated root causes. This research should reshape the current approach to fatal accident causation by creating a more holistic understanding of root causes for construction fatalities and how they interact together.