Offshore structures such as oil rigs, floating platforms, and wind turbines are vital to the energy and maritime sectors but are vulnerable to explosive incidents that can compromise their structural integrity. This study investigates the response of a fixed steel jacket offshore structure to blast loading, with a focus on internal explosions. Using a detailed three-dimensional finite element model developed with SACS 12.0 Connect Edition software, the study examines the impact of various blast scenarios on the structural behavior. The model incorporates comprehensive material properties and adheres to API RP 2A-WSD standards to evaluate the safety and resilience of the offshore platform under extreme conditions. The analysis includes a range of loading conditions—blast, wave, and wind—applied to different structural levels. Key findings reveal significant variations in displacement, shear stress, and axial stress across different stories, highlighting the critical need for enhanced design strategies to address internal blast effects. The study emphasizes the importance of robust design and advanced analytical methods to improve the safety and durability of offshore structures subjected to both internal and external explosive events.