Alopecia areata (AA) is a common form of localized, non-scarring hair loss. It is characterized by the loss of hair in patches, total loss of scalp hair (alopecia totalis), or total loss of body hair (alopecia universalis). The etiopathogenesis of the disease is still unclear, but there is evidence that autoimmunity and endocrine dysfunction may be involved. The aim of this study was to determine whether AA is statistically associated with thyroid autoimmunity. In this retrospective epidemiologic study, we compared the frequency of thyroid autoantibodies (thyroglobulin antibody, TgAb, and thyroid peroxidase antibody, TPAb) ATPO) in 70 AA patients and 30 healthy volunteers. Thyroid autoantibodies and thyroid hormones (thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH)) were measured in all subjects. Thyroid functional abnormalities were found in 8 (11.4%) AA patients. Positive autoimmune antibodies were associated with AA in 18 (25.7%) patients, with no significant association between the disease severity and presence of these antibodies. The frequency of thyroid autoantibodies was significantly higher in AA patients than in healthy controls (25.7% vs. 3.3%; p<0.05). Our findings pointed to a significant association between AA and thyroid autoimmunity and showed the tests to detect thyroid autoantibodies to be relevant in AA patients.