Background: Vitamin D insufficiency is associated with autoimmune and chronic inflammatory diseases such as tuberculosis and sarcoidosis. Objectives: To evaluate the vitamin D-dependent mechanisms of immunity and autoimmunity in different forms of pulmonary tuberculosis and sarcoidosis. Methods: We measured the serum levels of 25(OH)D and 1,25(OH)₂D, individual autoimmune profiles, plasma concentrations of cathelicidin, several hormones, and production of nine cytokines in patients with short- and long-duration tuberculosis and sarcoidosis. Results: The level of 25(OH)D was significantly decreased in all patients. Concentration of 1,25(OH)₂D was elevated only in sarcoidosis, prolactin content was augmented only in tuberculosis. We saw no expected increase of cathelicidin levels in tuberculosis and sarcoidosis. The individual mean immune reactivity levels of autoantibodies to 24 antigens were significantly lower in tuberculosis and sarcoidosis patients compared to healthy controls. Pronounced deviations from individual mean immune reactivity levels were found for several autoantigens in all patients. The induced production of interferon gamma-γ, interleukin (IL) 2, 17, and 8 by peripheral blood mononuclear cells was significantly increased in patients of both tuberculosis groups, but spontaneous production of tumor necrosis factor-α, IL-2, and IL-6 was lower in the tuberculosis patients than in healthy controls. We registered marked differences in the groups of tuberculosis patients. Conclusions: We demonstrated the role of vitamin D deficiency in poor cathelicidin response in tuberculosis and sarcoidosis. Both diseases are accompanied by significant changes in the autoimmune profile, probably related to the status of vitamin D and cytokine regulation.