The authors present a case of huge atypical choroid plexus papilloma in both lateral and third ventricles. A 2-year-old girl presented with lethargy and vomiting. Magnetic resonance images disclosed a huge enhancing mass, which probably arose from the left lateral ventricle and extended to the right lateral and the third ventricles. Total removal of the mass via the interhemispheric transcallosal approach was done. Histologically, an atypical choroid plexus papilloma was identified. Second operative treatment, subduro-peritoneal shunt, was performed due to postoperative subdural effusion. The patient was discharged two weeks after the second surgical procedure without a neurological deficit.