The oil and gas industry is a sector with a high level of occupational safety risk, especially in marine operations involving various types of support vessels. The high potential for danger requires the implementation of an effective occupational safety and health (OSH) system, not only through policies and procedures, but also through the improvement of safety knowledge, safety climate, and safety behaviour of the crew. However, the occurrence of marine incidents shows that safety control efforts are not yet fully optimal. This study aims to analyse the influence of safety knowledge and safety climate on safety performance with safety behaviour as a mediating variable in marine operations management at Pertamina Subholding Upstream. This study uses a quantitative approach with a survey method targeting marine operation support ship crews. This study uses a quantitative approach with the Structural Equation Modelling–Partial Least Squares (SEM-PLS) method. Data was obtained through questionnaires distributed to crews involved in marine operations. The results of the study indicate that safety knowledge and safety climate have a positive effect on safety performance, with safety climate being the dominant factor. Safety knowledge and safety climate also have a positive effect on safety behaviour and management support. Furthermore, safety behaviour and management support are proven to act as mediating variables that strengthen the relationship between safety knowledge and safety climate on safety performance. These findings emphasize the importance of strengthening safety knowledge, creating a conducive safety climate, and consistent management commitment to continuously improve occupational safety performance in marine oil and gas operations