Hypothyroidism is a frequently diagnosed endocrine disorder that has characteristic clinical signs and symptoms. Myopathy is one of the manifestations of hypothyroidism and relatively common. We report a case of Hoffmann's Syndrome due to hypothyroid myopathy documented by clinical features, laboratory findings and positive response to thyroid hormone replacement therapy. A man, age of 22, was diagnosed as having primary hypothyroidism at the age of five, had been describing progressive weakness in his arms and legs for two months and complained about generalized muscle cramps and pain. He was diagnosed with Hoffmann's syndrome with low levels of thyroid hormones and high levels of muscle enzymes. After six months of thyroid hormone replacement therapy, both the clinical picture and laboratory findings were remarkably improved.