This chapter investigates the bioaccumulation of heavy metals and toxic chemicals in mud crabs (Scylla spp.) and explores their implications for food web dynamics, environmental monitoring, and human health. Coastal ecosystems inhabited by Scylla spp. are increasingly exposed to pollutants such as lead (Pb), cadmium (Cd), mercury (Hg), and polycyclic aromatic hydrocarbons (PAHs), primarily from industrial, agricultural, and urban sources. These contaminants accumulate in various crab tissues, most notably the hepatopancreas, and are subsequently transferred to higher trophic levels, raising ecological and public health concerns. By examining regional case studies, this chapter highlights spatial variability in contamination levels and establishes mud crabs as promising bioindicators for estuarine and mangrove pollution. It further discusses methodological advances in monitoring, including biochemical and molecular biomarkers, and presents policy recommendations for sustainable fisheries and pollution mitigation. The findings underscore the importance of integrating ecological data with management practices to safeguard biodiversity, food safety, and coastal livelihoods.