<p>Choroid plexus volume change has been suggested as a biomarker for the course of various neurological diseases. However, its role in sleep disorders remains unclear. We analyzed choroid plexus volume changes in patients with isolated rapid eye movement sleep behavior disorder (iRBD) compared with healthy controls. We enrolled 27 patients with iRBD and 27 healthy controls. All participants underwent brain magnetic resonance imaging (MRI), including three-dimensional T1-weighted imaging suitable for volumetric analysis. iRBD was diagnosed based on overnight polysomnography and corresponding clinical history. We compared the choroid plexus volume between patients with iRBD and healthy controls, and investigated the relationship between choroid plexus volume and polysomnographic findings. The mean choroid plexus volume was significantly larger in patients with iRBD than in healthy controls (2.379% vs. 2.116%, <i>p</i> = 0.002). No significant correlation was observed between choroid plexus volume and polysomnographic findings in patients with iRBD. Patients with iRBD demonstrated choroid plexus enlargement compared with healthy controls. This finding could be related with glymphatic system dysfunction in this population.</p>