We report a rare case of an isolated critical tricuspid regurgitation due to rupture of a papillary muscle. This patient presented with a cyanosis immediately after birth. Despite mechanical ventilation and medical management to decrease the pulmonary vascular resistance, the low cardiac output persisted, along with the cyanosis. Repair of the tricuspid valve was performed, using an artificial tendinous cord, on the 4th day of life. The short-term result of the surgery is satisfactory, but the patient requires long-term follow-up.