Microplastic pollution represents a significant and growing environmental threat to aquatic ecosystems and human health. This chapter comprehensively reviews the bioaccumulation of microplastics in fish, exploring their sources, pathways, and potential toxicological impacts. Both primary and secondary microplastics originate from various anthropogenic activities, entering aquatic systems through domestic sewage, industrial discharge, and surface runoff. Once ingested by aquatic organisms, including commercially important fish species, microplastics persist in the gastrointestinal tract and can translocate to organs such as liver, kidneys, and muscle tissue. This bioaccumulation facilitates trophic transfer through the food web, raising concerns about contamination of fishery products consumed by humans. The physical presence of microplastics causes digestive blockage, reduced feeding, and developmental abnormalities in fish, while adsorbed environmental pollutants contribute to oxidative stress, inflammation, and endocrine disruption. Emerging evidence indicates the widespread presence of microplastics in human tissues, highlighting an urgent need to understand exposure pathways and health effects. The chapter also discusses existing regulatory frameworks, their limitations, and gaps in managing microplastic pollution. Addressing these challenges requires integrated research efforts on the environmental fate of microplastics, advancements in purification technologies, and the promotion of alternatives to conventional plastics to mitigate ecological and human health risks.