A 76-year-old woman was admitted due to hyperthyroidism-associated congestive heart failure with acute exacerbation, complicated with bilateral massive pleural effusion. After successful antithyroid treatment, there was no more heart failure episode in a 3-year follow-up period. Congestive heart failure is not a common manifestation of hyperthyroidism. However, most of the patients presenting with congestive heart failure as the main symptom of hyperthyroidism have had sinus tachycardia or atrial fibrillation. This case, presented as isolated congestive heart failure with bilateral massive pleural effusion without tachycardia as the manifestation of hyperthyroidism, was very rare. In conclusion, if an elderly patient develops unexplained congestive heart failure, we should take hyperthyroidism into consideration even the heart rate shows normal sinus rhythm.