Research suggests a connection between idiopathic intracranial hypertension and the cerebral glymphatic system. We hypothesized that visible dilated perivascular spaces, possible glymphatic pathways, would be more prevalent in patients with idiopathic intracranial hypertension. This prevalence could provide a biomarker and add evidence to the glymphatic connection in the pathogenesis of idiopathic intracranial hypertension. We evaluated 36 adult (older than 21 years of age) patients with idiopathic intracranial hypertension and 19 controls, 21-69 years of age, who underwent a standardized MR imaging protocol that included high-resolution precontrast T2- and T1-weighted images. All patients had complete neuro-ophthalmic examinations for papilledema. The number of visible perivascular spaces was evaluated using a comprehensive 4-point qualitative rating scale, which graded the number of visible perivascular spaces in the centrum semiovale and basal ganglia; a 2-point scale was used for the midbrain. Readers were blinded to patient diagnoses. Continuous variables were compared using a Student test. The mean number of visible perivascular spaces overall was greater in the idiopathic intracranial hypertension group than in controls (4.5 SD, 1.9 versus 2.9 SD, 1.9, respectively; = .004). This finding was significant for centrum semiovale idiopathic intracranial hypertension (2.3 SD, 1.4 versus controls, 1.3 SD, 1.1, = .003) and basal ganglia idiopathic intracranial hypertension (1.7 SD, 0.6 versus controls, 1.2 SD, 0.7, = .009). There was no significant difference in midbrain idiopathic intracranial hypertension (0.5 SD, 0.5 versus controls, 0.4 SD, 0.5, = .47). Idiopathic intracranial hypertension is associated with an increased number of visible intracranial perivascular spaces. This finding provides insight into the pathophysiology of idiopathic intracranial hypertension, suggesting a possible relationship between idiopathic intracranial hypertension and glymphatic dysfunction and providing another useful biomarker for the disease.