Riedel’s thyroiditis is a rare form of infiltrative and inflammatory disease of the thyroid gland and can be associated with systemic fibrotic processes, Hashimoto thyroiditis and Graves disease. Riedel thyroiditis in combination with Graves disease however,is very rare. A 57-year-old woman with a past medical history significant for Graves disease diagnosed 30 years ago presented with an enlarging neck mass and voice changes. Due to suspicion of malignancy, thyroidectomy was performed. Histopathologic examination revealed Riedel thyroiditis. To our knowledge, the association of Riedel thyroiditis with Graves disease has not yet been reported in our country. Here we report a patient with Riedel thyroiditis evolved from antecedent Graves disease.