Background: In Parkinson’s disease (PD), mounting evidence implicates degeneration of cholinergic systems in cognitive and gait decline. The Nucleus Basalis of Meynert (NBM) is a major cholinergic nucleus with widespread cortical projections. We hypothesized that atrophy of the NBM is correlated with cognitive phenotypes and gait measures in PD. Methods: Subjects from the COMPASS-ND study (20 controls and 79 PD patients) were studied. Clinical measures included cognitive diagnosis (MCI, dementia) and quantitative gait parameters with dual task gait. Manual region of interest measurement of the NBM was performed on T1 MRI scans. NBM volumes were analyzed against clinical measures. Results: PD-MCI and PD-dementia patients had greater dual task costs to gait speed when performing serial 7s (mean difference -12%, p=0.02; -11%, p=0.04) and animal fluency tasks (mean difference -9%, p=0.02; -15%, p<.001) compared to controls. Reduced normalized NBM volume was associated with PD-MCI (mean difference 0.34, p=0.04) and PD-dementia (mean difference 0.55, p<0.001) phenotypes. NBM volume was weakly correlated with gait velocity (r2 0.06, p=0.01) and dual task cost to gait velocity with animal fluency (r2 0.06, p=0.02). Conclusions: NBM atrophy is associated with cognitive decline in PD and may be responsible for cognitive aspects of gait performance.