Background: A retained surgical sponge, an extremely rare occurrence after cardiac surgery, can trigger a granulomatous reaction and form a sizeable mass or gossypiboma. We report the incidental operative finding of a gossypiboma 11 years after repair of Ebstein anomaly.Case Report: A 24-year-old man, who had previously undergone tricuspid annuloplasty for Ebstein anomaly 11 years earlier at another institution, was referred for recurrent severe tricuspid regurgitation. During the dissection along the superior vena cava and the right atrium, we entered 2 cystic cavities that exuded a pus-like material, which was sent for culture. Mesh from a retained surgical sponge (gossypiboma) was identified. After complete debridement and administration of vancomycin, the tricuspid valve was repaired. Antibiotics were continued until culture results were confirmed to be negative. The patient's postoperative course was uneventful, and he presented no signs of infection.Conclusions: We report a rare case of incidentally found gossypiboma after cardiac surgery.