We report a novel case of a mixed choroid plexus papilloma (CPP) and ependymoma with cartilaginous differentiation. This kind of mixed tumor has not been previously reported in the English literature. The patient was a 5-year-old girl, who presented with a 1-week history of fever and numbness of the right lower limb. Magnetic resonance imaging of the brain with gadolinium revealed a heterogeneously enhancing mass in the occipital horn of the left lateral ventricle. Histologically, the tumor showed an intermixed CPP area and a low-grade papillary ependymoma-like area, which was studded with cartilage islands and psammoma bodies. In many foci, direct transition of CPP and ependymoma was observed, but there were no high-grade features. We report this novel case, describe the unique microscopic and immunohistochemical features, and speculate on the pathogenesis.