Owing to global energy consumption and increasingly severe environmental challenges, the development of clean and sustainable hydrogen technologies has become a research hotspot. Seawater electrolysis exhibits great potential due to its abundant resources and environmental friendliness. However, the seawater composition complexity (e.g., Cl^-, Mg²⁺, etc.) poses significant challenges to the electrocatalyst behaviors. Transition metal nitrides (TMNs), owing to high electrical conductivity, noble-metal-like electronic structures, and excellent corrosion resistance, have emerged as promising alternatives to noble metals. This review systematically summarizes recent advancements of TMN-based electrocatalysts for seawater electrolysis, with a focus on their catalytic mechanisms, structural design strategies, and performance optimization in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Studies demonstrate that heterointerface engineering, defect regulation, and surface modification can significantly enhance the activity and chloride corrosion resistance of TMNs. Although challenges remain in achieving industrial-scale current density stability and mass production feasibility, multiscale synergistic optimization and innovative system integration position TMNs as promising core materials for efficient and cost-effective seawater electrolysis, thereby providing critical technological support for a green hydrogen economy.