Autoimmune thyroiditis (HT), also known as chronic autoimmune thyroiditis, is the most common organ-specific autoimmune disorder, characterized by self-tissue destruction due to an altered adaptive immune response. Vitamin D plays an immunomodulatory role, potentially promoting immune tolerance. This review explores the relationship between vitamin D status and HT, as well as the role of vitamin D supplementation in reducing HT risk by modulating the immune system. Studies show that vitamin D levels are significantly lower in HT patients compared to healthy individuals. Supplementation with cholecalciferol in HT patients with vitamin D deficiency leads to a significant decrease in thyroid autoantibody titers. Vitamin D influences both innate and adaptive immune systems, modulating immune cell activation, differentiation, and function. It reduces pro-inflammatory cytokines and enhances anti-inflammatory cytokines, inhibiting immune responses that lead to autoimmunity. Vitamin D deficiency may compromise immune function and increase the risk of autoimmune diseases. Observational studies suggest a link between low vitamin D levels and increased HT risk, though the exact mechanisms remain unclear. Randomized controlled trials are needed to confirm the benefits of vitamin D supplementation in HT. Vitamin D may help reduce thyroid autoantibodies and improve thyroid function, potentially preventing or treating autoimmune thyroid diseases. However, more research is required to determine its effectiveness in HT treatment and prevention.Autoimmune thyroiditis (HT), also known as chronic autoimmune thyroiditis, is the most common organ-specific autoimmune disorder, characterized by self-tissue destruction due to an altered adaptive immune response. Vitamin D plays an immunomodulatory role, potentially promoting immune tolerance. This review explores the relationship between vitamin D status and HT, as well as the role of vitamin D supplementation in reducing HT risk by modulating the immune system. Studies show that vitamin D levels are significantly lower in HT patients compared to healthy individuals. Supplementation with cholecalciferol in HT patients with vitamin D deficiency leads to a significant decrease in thyroid autoantibody titers. Vitamin D influences both innate and adaptive immune systems, modulating immune cell activation, differentiation, and function. It reduces pro-inflammatory cytokines and enhances anti-inflammatory cytokines, inhibiting immune responses that lead to autoimmunity. Vitamin D deficiency may compromise immune function and increase the risk of autoimmune diseases. Observational studies suggest a link between low vitamin D levels and increased HT risk, though the exact mechanisms remain unclear. Randomized controlled trials are needed to confirm the benefits of vitamin D supplementation in HT. Vitamin D may help reduce thyroid autoantibodies and improve thyroid function, potentially preventing or treating autoimmune thyroid diseases. However, more research is required to determine its effectiveness in HT treatment and prevention.