Selenium is important for the proper functioning of the human body. This element is closely related to the proper functioning of the thyroid gland and normal metabolism of thyroid hormones. Moreover, it plays a role in the treatment of diseases affecting this organ. The present work was aimed at collecting recent reports on the effect of selenium supplementation on the course of Hashimoto’s disease and was an attempt to explain how this element can affect the thyroid gland. The paper presents the effect of selenium supplementation at various stages of Hashimoto’s disease and the possible molecular basis for the observed biochemical and therapeutic changes. The studies presented by the authors describe the effect of selenium on, inter alia, the level of antithyroid antibodies, proinflammatory factors and echogenicity of the thyroid in people with Hashimoto’s disease. The article also discusses interesting molecular studies describing the importance of selenium in the process of apoptosis, or in the modification of the HLA expression on thyroid cells. Selenium is probably involved in the modification of autoimmune reactions in the affected thyroid gland. What is more, thanks to its special antioxidant properties, selenium reduces chronic inflammation in the thyroid with Hashimoto’s disease. It is definitely worth paying attention to this micronutrient because it may improve the therapy of chronic autoimmune thyroiditis and, maybe in some time, after more clinical investigation, it will become an important part of the therapy in this disease entity.