Congestive heart failure due to hypocalcemia is rare. We describe a 36-year-old woman with hypocalcemia who presented with cardiomealy and congestive heart failure. Her serum calcium was 4.8 mg/dl and phosphorous 6.1 mg/dl. Idiopathic dilated cardiomyopathy was diagnosed by cardiac catheterization and right ventricular biopsy. Her decompensated heart improved gradually after calcium supplements and conventional treatment for heart failure. We provpose the cause of her heart failure was iatrogenic hypoparathyroicism induced hypocalcemia. We suggest that physicaians should be aware that hypocalcemia can be a reversible cause of dilated cardiomyopathy and congestive heart failure especially in patients who have had a radical thyroidectomy.