Microwave ablation therapy has been attracting great attention due to its advantages such as low complication rate, good cosmetic results, and effective nodule shrinking. Although the effect of thermal ablation therapy on the nodule volume reduction rate has been shown several studies, a limited number of papers has been reported for the effects of microwave ablation (MWA) on thyroid function tests.The aim of this study was to investigate the short- and long-term effects of MWA therapy on thyroid function tests (TFTs), thyroglobulin (Tg) and thyroid autoantibodies in euthyroid patients.Demographic data of the patients, TFTs, Tg, thyroid autoantibodies, and thyroid volume of the nodules were recorded before the procedure and follow-up. Any differences in serum thyroid hormone levels were investigated in pre-, post-, and 6-month follow-up periods before and after MWA.The difference between all thyroid hormone levels at pre MWA and 24 h after MWA were statistically significant (P <0.001). FT3 (4.62) pmol/L and FT4 (10.81) pmol/L median levels increased significantly (P <0.001) while TSH levels decreased at 24 h after MWA (P <0.001). Thyroid antibodies levels were not statistically different at 6-month (P >0.05) whereas Tg levels decreased (P <0.001) compared to pre MWA.While no significant effect was observed at 6-month, the effect of MWA on thyroid function tests was prominent at 24 h.