Pulmonary hypertension in adults with hyperthyroidism is increasingly being reported. Although the mechanism is uncertain, the reversal of pulmonary hypertension following restoration to an euthyroid state supports a causal relationship. This case report is of a 43-year-old woman who presented with Graves disease and right ventricular failure. Echocardiography showed severe pulmonary hypertension, moderate to severe tricuspid regurgitation, normal left heart function and a negative bubble contrast study. Carbimazole therapy was instituted along with diuretics and captopril. The patient was followed for a period of 14 months. Clinical and biochemical euthyroidism was attained after 4 months of treatment. Resolution of right ventricular failure and normalization of pulmonary artery pressure occurred 11 and 14 months after initiation of therapy, respectively. Investigating thyroid status in patients with pulmonary hypertension is recommended. In patients with hyperthyroidism and (otherwise unexplained) pulmonary hypertension, restoration of euthyroidism may cure right ventricular failure and restore normal pulmonary artery pressure.