Anethum graveolens L. is used in the treatment of numerous diseases. But there is limited data about the Anethum graveolens efficiency in thyroid tissue.The aim of this study is to assess the functional and histopathological changes in thyroid tissues from rats treated with Anethum graveolens L. extract.This is an experimental animal study and duration of the study was 30 days.Twenty-eight female Wistar Albino rats were divided into four equal groups. A gavage of Anethum graveolens L. extract at 0, 50, 150 and 300 mg/kg/day doses were given to the rats with 1 mL 0.9% NaCl, respectively, for 30 days. Blood was taken at day 0, 15 and 30. fT3, fT4, TSH values and antioxidant efficiency were observed. Also the thyroidectomy tissue was assessed histopathologically.There is no difference observed in the fT3, fT4 and TSH values of groups 1, 2 and 3 at day 1, 15 and 30 (p>0.05); however, in group 4, TSH value decreased on days 15 and 30 when compared to day 1 and the other groups (p0.05).Anethum graveolens L. extract is effective on both the function and the histology of thyroid tissue but it has no effect on antioxidant status.