A 64-year-old female without symptoms of heart failure was diagnosed with a two-chambered right ventricle (TCRV) during examination of a heart murmur and cardiac enlargement, for which surgery was performed. Under cardiopulmonary bypass and cardiac arrest, we first performed a right atrium and pulmonary artery incision and observed the right ventricle through the tricuspid and pulmonary valves, although we could not obtain a sufficient view of the right ventricular outflow tract. After subsequently incising the right ventricular outflow tract and the anomalous muscle bundle, the right ventricular outflow tract was patch-enlarged using a bovine cardiovascular membrane. After weaning from cardiopulmonary bypass, disappearance of the pressure gradient in the right ventricular outflow tract was confirmed. The patient's postoperative course was uneventful without any complications including arrhythmia.