Asymmetric ventriculomegly due to idiopathic occlusion of the foramen of Monro is rare. Such patients present with clinical features of raised intracranial pressure (ICP). Presentation as chronic headache has not been previously described. In the absence of raised ICP, pursuing surgical treatment raises a clinical dilemma as the headache may be a primary headache with no improvement after surgery. A 21-year-old woman presented with chronic headache. She was found to have asymmetric ventriculomegaly due to the occlusion of the foramen of Monro. She underwent endoscopic septostomy and widening of the foramen of Monro. Her headache subsided after surgery. At 15 months of follow-up, she was free from headache without medications. Unilateral occlusion of the foramen of Monro can present with asymmetric ventriculomegaly resulting in chronic headache. Though the symptoms of raised ICP may not be present, still endoscopic relief of ventriculomegaly leads to cure of headache.