In recent years, microplastics have attracted the attention of the scientific community as a potentially dangerous factor affecting human health. This review is devoted to the analysis of the sources of microplastics, their routes of entry into the body, as well as possible biological effects. Mechanisms of toxicity are reviewed, including inflammatory responses, oxidative stress, damage to cellular structures, and effects on the endocrine system. Particular attention is paid to the effect of microplastics on the digestive, respiratory, nervous, and endocrine systems. Data are presented on the accumulation of microplastics in tissues and its possible connection with the development of various diseases, including cancer and neurodegenerative pathologies. Finally, prospects for further research and the need to develop strategies to reduce the impact of microplastics on the human body are discussed.