Background: Gastrointestinal dysfunction and related clinical symptoms are common in Parkinson’s disease (PD), but the underlying mechanisms are still poorly understood. Objective: In this study, we investigated how PD affects the postprandial vascular response in the splanchnic circulation. Methods: 23 patients with PD in the “ON-medication” state and 23 age- and sex-matched healthy control participants underwent serial phase-contrast magnetic resonance imaging (PC-MRI) to measure the postprandial blood flow response in the superior mesenteric artery (SMA). Participants ingested a standardized liquid test meal (∼400 kcal) and underwent four PC-MRI runs within the following hour. Each PC-MRI run consisted of six consecutive measurements of SMA blood flow. Results: In both groups, standardized food intake triggered an increase of blood flow in the SMA, but absolute and relative increases in blood flow were attenuated in patients compared to the control group (p