A 12-month-old girl presented with a rare atypical choroid plexus papilloma manifesting as conscious disturbance and vomiting. Magnetic resonance (MR) imaging revealed a well-delineated 5 x 6-cm lobulate mass in the right lateral ventricle. Only partial removal of the tumor was performed because of excessive intraoperative hemorrhage at the first surgery. The histological diagnosis was atypical choroid plexus papilloma. To control the intraoperative hemorrhage, embolization of the feeding artery was performed before the second surgery, and the tumor was macroscopically totally removed. MR imaging disclosed a small residual tumor which showed relatively rapid growth. The patient underwent the third removal 5 months after the second surgery. Two months later, MR imaging showed a cystic lesion with a small nodule adjacent to the midbrain, indicating dissemination of the tumor. The lesion was successfully treated with chemotherapy. Atypical choroid plexus papilloma was recently defined in the classification of the World Health Organization, so clinical data based on these criteria are lacking to establish the therapeutic strategy. Total resection of atypical choroid plexus papilloma is the most reliable treatment at present. However, postoperative chemotherapy should be considered for recurrence or dissemination.