A patient with previously diagnosed Graves’ hyperthyroidism had a transient episode of thyrotoxicosis late in gestation. This was associated with minimally palpable thyroid tissue, a rise in TgAb as well as TPOAb and negative TRAb(ECLIA) and TSAb(EIA). This case would suggest that patient with previously diagnosed Graves’ disease can have thyrotoxicosis without TRAb which is often found in painless thyroiditis occurring during the remission of Graves’ disease. In addition, an alternative cause for spontaneously resolving thyrotoxicosis was not discovered except painless thyroiditis. To our knowledge, this is the first case report of gestational thyrotoxic syndrome occurring late in gestation, but the specific mechanism has not been settled.