Amyloidosis is an abnormal extracellular deposit of amyloid in various organs of the body. Amyloid goiter, defined by a clinically detectable thyroid enlargement due to amyloid deposition, is a rare cause of hyperthyroidism. We report the case of amyloid goiter mimicking Graves' disease in a 62-year-old woman. Graves' disease was diagnosed by diffuse goiter, hyperthyroidism, and positive TSH receptor antibody. Total thyroidectomy was planned due to progression of Graves' disease and respiratory distress. At surgery thyroid gland was very friable and fragmented like cobblestones when grasped with forceps. A diagnosis of amyloid goiter was established by the presence of diffuse amyloid deposits in the parafollicular areas. After systemic evaluation for amyloidosis, coexisting both multiple myeloma and systemic amyloidosis involving kidney and heart were detected. She underwent palliative chemotherapy but disease progressed. Amyloid goiter might be suspected in patient with thyroid enlargement and concomitant systemic disease such as renal or heart failure.