Amyloid accumulation in the thyroid gland leading to a clinically detectable mass, known as amyloid goiter, is a rare condition associated with primary amyloidosis. Moreover, a localized primary amyloid goiter involving only the thyroid gland is rarer still. Here, we report a patient with a localized primary amyloid goiter that had grown rapidly, causing dysphagia and dyspnea on exercise, and confused us with malignancy such as anaplastic carcinoma. After surgery, no further symptoms occurred. A diagnosis of amyloid goiter was established on microscopic examination. In patients with a rapidly enlarging thyroid gland presenting with dysphagia, dyspnea, or hoarseness, amyloid goiter and malignancy should both be suspected, even when systemic amyloidosis is not suspected.