Patients with idiopathic intracranial hypertension (IIH) frequently have coexisting obstructive sleep apnea (OSA). We aimed to determine if the prevalence and severity of OSA is greater in patients with IIH than would be expected, given their other risk factors for OSA. We included 24 patients (20 women, four men) with newly-diagnosed IIH who had undergone overnight polysomnography. We calculated the expected apnea-hypopnea index (AHI) for each patient, based on their age, sex, race, body mass index (BMI), and menopausal status, using a model derived from 1,741 randomly-sampled members of the general population who had undergone overnight polysomnography. We compared the AHI values obtained from polysomnography with those predicted by the model using a paired t test. Our study had 80 % power to detect a 10-unit change in mean AHI at α = 0.05. Eight patients (33.3 %; six women, two men) had OSA by polysomnography. AHIs from polysomnography were not significantly different from those predicted by the model (mean difference 3.5, 95 % CI: -3.0-9.9, p = 0.28). We conclude that the prevalence and severity of OSA in IIH patients is no greater than would be expected for their age, sex, race, BMI, and menopausal status. It remains unclear whether the presence or treatment of OSA influences the clinical course of IIH.