<p>Wetlands are critical sites for the biogeochemical cycling of mercury, where the unique anaerobic environment and rich microbial communities significantly enhance the methylation process, producing the highly toxic methylmercury (MeHg), which poses serious threats to ecosystems and human health. Although previous studies have revealed some mechanisms of mercury methylation, issues remain, such as unclear differences in methylation mechanisms between natural and artificial wetlands and insufficient analysis of multi-factorial interactions. This paper systematically reviews the mechanisms of mercury methylation in wetlands and its environmental influencing factors, aiming to clarify the sources and risks of mercury, elucidate its migration and transformation characteristics, 11 reveal the driving factors of methylation, and propose prevention and control strategies. The main conclusions include: (1) The sources of mercury pollution in wetlands are complex, influenced by multiple factors such as surface runoff, atmospheric deposition, and geological background, with a significant contribution from human activities; (2) The forms of mercury (e.g., Hg²⁺, Hg⁰, and MeHg) and their bioavailability are key determinants of methylation efficiency; (3) Sulfate-reducing bacteria (SRB) and iron-reducing bacteria (FeRB) are the primary methylating microorganisms, whose activity is regulated by the hgcAB gene and significantly affected by environmental factors such as pH, organic matter, temperature, and salinity; (4) Methylmercury poses major ecological risks through the biomagnification effect in the food chain, particularly in acidic (pH 4–6) and organic-rich environments where the risk is heightened. Current research still lacks sufficient understanding of the synergistic effects of microbial communities and their long-term dynamics, necessitating future studies that integrate multi-omics technologies and in situ characterization methods to deepen mechanistic research. This study provides a scientific basis for the risk assessment and prevention of mercury pollution in wetlands, which is of significant importance for global mercury management and ecosystem protection.</p> Graphical abstract <p></p>