Diabetes mellitus type 1 (DM1) and type 2 (DM2) is one of the most common chronic diseases with high rates of morbidity and mortality. Insulin replacement therapy and other various hypoglycemic means have been used for more than 90 years to control high blood glucose levels, but they cannot accurately mimic the secretion of endogenous insulin, can cause reactive hypoglycemia, and do not exclude the risk of secondary complications of diabetes (nephropathy, neuropathy, retinopathy, vascular pathology). The introduction of new scientific achievements into clinical practice in the future allows optimizing the treatment for diabetes and its complications, which can significantly improve the quality of life of many patients. A very promising method of DM therapy is the use of stem cells (SC) as an almost unlimited source of physiologically competent substitute for primary islets of Langerhans. SC can transform (specialize) into any cell of the body and, unlike others, can divide an indefinite number of times. This allows SC to maintain a certain number of their population and allows for the formation of a whole hierarchy of SC in the body, which are stored in certain depots. And, finally, SC are characterized by the Homing effect— the ability to find the damaged zone and fix itself in it, filling the lost function when introduced into the body. A number of studies and recent meta-analyses suggest that C-peptide, HbA1c levels, and daily insulin requirements improve after treatment of DM with stem cells, meaning that SC therapy may be a safe and effective intervention for some individuals with DM. In DM1, bone marrow hematopoietic SC are a good source of SC transplantation. In DM2, HbA1c and daily insulin requirements were significantly improved after mesenchymal SC therapy, and bone marrow mononuclear cell therapy significantly reduced insulin requirements and improved C-peptide levels. These encouraging results require confirmation in large, randomized, double-blind studies, as well as with longer follow-up periods to clearly recommend stem cell-based therapy as the standard of DM management.