•A meticulous investigation into the casual factors contributing to construction accidents in a developing country is investigated.•A novel fuzzy Delphi method for identifying and prioritizing the critical causes is proposed.•The cause-and-effect relationships among the critical casual factors are unraveled using the FDEMATEL technique.•Twenty-three sub-causes are seen to be the major culprits for the occurrence of related accidents.•Organizational and workplace and environmental causes turn out to be the most influential causes. Though some studies have explored the causes of accidents on construction sites, the interdependency among the underlying causes remains elusive. This undermines the efficacy of any decision made by safety experts in reducing accidents’ impact. To fill this gap, a hybrid fuzzy-based framework is developed in this study to comprehensively identify and prioritize critical causes, as well as map interrelationships among these causes. The proposed framework is based on the infusion of the Pentagonal Fuzzy Delphi Method (PFDM) and Fuzzy DEMATEL techniques. Findings show that six main causes and twenty-three corresponding sub-causes (out of forty-seven identified ones) are the major culprits for the occurrence of related accidents. Furthermore, it was revealed that “organizational” and “workplace and environmental” causes turn out to be the most influential causes, while inappropriate safety guidelines and policies, poor safety management system, poor safety culture, poor safety knowledge of management team, the financial instability of firms, and corruption were the predominant sub-causes affecting the related accidents’ impact. To validate findings, several interviews with senior experts are undertaken. The outcomes of this study are vital for the concerned safety decision-makers by highlighting the influential causes debilitating the safety and health of involved workers.