A 76-year-old female patient complained of intermittent palpitation, shortness of breath, and orthopnea for 10 days. The patient was found to have cardiomegaly, left ventricular dilatation secondary to moderate regurgitation, with impaired ventricular dysfunction and persistent sinus tachycardia. The patient also had a nodular goiter with increased uptake on radionuclide scan on the right side of the thyroid gland, low serum thyroid-stimulating hormone, with normal triiodothyronine, and free thyroxine. Plummer's disease with ventricular dysfunction was diagnosed. We present this rare case and a review of the literature.