It is important to establish all the causes of marine accidents, but this is sometimes quite difficult. Therefore, analyzing the causes by examining as many accidents as possible using a common classification system and submission of proposals is extremely essential. Overall, the study is an examination of collision and grounding accidents using the Human Factors Analysis and Classification System (HFACS). In the first phase of the study, the frequency and distribution of the causes of collision and grounding accidents were examined by HFACS categories. In the second phase, unsafe acts, which have been identified as the most important categories, and preconditions for unsafe acts are evaluated by bridge crew structure. The Chi-Square Test of Compliance and Independence and Simple Correspondence Analysis are used as statistical methods. As a result of study, the most important causes are identified as human factor differences between collision and grounding accidents, decision errors, resource management deficiencies, violations, skill-based errors and miscommunication.