Mercury (Hg) is a pervasive environmental contaminant with high bioavailability and toxicity, accumulating in aquatic food chains and posing significant risks to human health through seafood consumption. This systematic review aims to collect evidence on Hg bioaccumulation in seafood across Europe, assessing species that exceed legal limits. A total of 74 studies were identified on bioaccumulation among marine fish and seafood from European and adjacent seas, published between 2000 and 2024. Findings highlight that methylmercury (MeHg) constitutes the majority of total Hg in fish species, with concentrations often exceeding EU regulatory limits, especially in the Adriatic and Iberian areas. In general, teleosts exhibit higher tissue concentrations of both MeHg and total Hg compared to either selachians or mollusks. Species likely to exceed their legal limits are larger, apex predators, e.g., tuna, swordfish, and sharks, as well as benthic species, e.g., monkfish and mullet. In recent years, there has been a decrease in mercury contamination, probably due to agreed international regulations. However, significant regional variations still persist in Europe. To mitigate Hg contamination in seafood and ensure food safety, this study highlights the need for ongoing monitoring and management strategies, the interplay of environmental factors, food web dynamics, and species-specific biological characteristics.