Post-contrast T1 changes (ΔT1) on brain MRI may reflect alterations in cerebrospinal fluid dynamics and microvascular exchange in movement disorders. We investigated regional post-contrast ΔT1 differences in patients with idiopathic Parkinson's disease (IPD) and essential tremor (ET). In this retrospective single-center study, 277 patients who underwent brain MRI for suspected movement disorders between November 2023 and February 2025 were classified as ET (n = 109), early IPD (n = 81), or advanced IPD (n = 87). Post-contrast ΔT1 values were calculated by subtracting pre-contrast from post-contrast T1 measurements in the choroid plexus (CP), basal ganglia perivascular spaces, cerebral cortex, cerebellar cortex, and thalamus. Advanced IPD demonstrated significantly greater T1 shortening in the CP compared with ET, while showing reduced T1 shortening in the cerebellar cortex and thalamus. No significant differences were observed in other regions. These findings suggest region-specific alterations in contrast kinetics in advanced IPD, potentially reflecting disease-related changes in contrast distribution and microvascular permeability. Quantitative post-contrast T1 mapping may provide complementary imaging markers for distinguishing Parkinson's disease from essential tremor.