A 59-year-old man was admitted because of congestive heart failure. He was suspected to have acromegaly, and magnetic resonance imaging revealed a pituitary macroadenoma. Endocrine examination revealed elevated plasma levels of growth hormone (GH) and insulin-like growth factor (IGF)-1, and an oral glucose tolerance test failed to suppress plasma GH levels, consistent with the diagnosis of GH-producing pituitary tumor. Treatment with octreotide, followed by transsphenoidal surgery resulted in normalization of plasma GH/IGF-1 levels, accompanied by the improvement of cardiac function. Thus, it is suggested that excess GH/IGF-1 axis is involved in the development of acromegaly-related cardiomyopathy in the present case.