The authors report an unusual case of a 2-year-old boy with a 3-month history of episodic rightward anterolateral head tilt and large-amplitude positional anteroposterior head bobbing reminiscent of bobble-head doll syndrome. This child experienced a sudden onset of drop attacks and then, within several hours, deep coma. The causative lesion was a contrast-enhancing, partially cystic third ventricular mass, which ultimately obstructed the aqueduct, producing profound obstructive hydrocephalus. An emergency ventriculostomy and endoscopic fenestration of the septum pellucidum was performed. Four days later, the tumor was completely resected by a transcallosal-transforaminal approach. The lesion was freely mobile within the third ventricle and contained a large cyst within its posterior pole; following drainage of the cyst, the lesion was easily delivered through the foramen of Monro. The histopathological diagnosis was choroid plexus papilloma. The child's neurological deficits, head tilt, and head bobbing resolved immediately after operation. To the best of the authors' knowledge, this represents the first well-documented report of bobble-head doll syndrome and drop attacks secondary to a choroid plexus papilloma. The highly mobile nature of the cystic lesion presumably led to its intermittent impaction within the foramen of Monro and/or proximal aqueduct; this produced the intermittent head tilt and bobble-head symptoms and, ultimately, resulted in acute obstruction of the aqueduct, causing the child's precipitous neurological decline.