Parkinson’s disease (PD) is characterized by neurodegeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNc). The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin can induce Parkinson syndrome in primate models. We evaluated the nigrostriatal (NS) pathway degeneration in MPTP Squirrel monkeys using diffusion MRI. The results showed significantly increased fractional anisotropy in all NS regions of the MPTP group (SN, caudate and putamen regions). Axial diffusivity also significantly increased in the SN and caudate regions, while radial diffusivities did not show any differences, except a significantly decreased λ3 in the putamen. Those results should help develop preclinical evaluation of PD therapeutics.