Isolated right ventricular hypoplasia is a rare clinical entity. We describe a case of right ventricular hypoplasia, single atrium and spongy myocardium of left ventricle. The volume of right ventricle was half the volume of left ventricle and z-value of tricuspid valve was -4 preoperatively The patient, 6-year-old boy, underwent atrial partitioning with 3 mm fenestration, Postoperative course was smooth and he tolerated the biventricular state well during follow-up. Follow-up catherterization was done 27 months later The tricuspid valve grew well (z-value= -0.4) and atrial septal fenestration is closed spontaneously. This article reports a case of successful biventricular repair in a patient with isolated right ventricular hypoplasia.