Right ventricular failure can be secondary to right ventricular ischemia, pulmonary or tricuspid valvular disease, myocardial shunts, cardiomyopathy, acute and chronic pulmonary hypertension, myocarditis and pericardial disease and it generally carries a poor prognosis. Thyrotoxicosis is a clinical state resulting from high thyroid hormone action in tissues generally due to high thyroid hormone levels. The association between severe hyperthyroidism and high-output heart failure is well-known. Less widespread is the concept that hyperthyroid patients, irrespective of coexisting diseases and through mechanisms not fully elucidated, are at higher risk for pulmonary hypertension and right heart failure, both reversible with the achievement of euthyroidism and associated with a good prognosis. We describe the case of a 44-year-old woman with right ventricular failure and moderate pulmonary hypertension in the setting of thyrotoxicosis, which resolved rapidly after antithyroid treatment. The potential mechanisms underlying this condition will also be discussed.