We encountered a case of multiple system atrophy parkinsonian subtype (MSA-P) with right-dominant parkinsonism in the early stage of the disease. Atrophy of the posterolateral putamen and iron deposition are the neuropathological hallmark of MSA-P. Coronal fluid-attenuated inversion-recovery (FLAIR) images showed atrophy and iron deposition in the left posterior putamen contralateral to the clinical dominant side in the early phase. Atrophy in the posterior putamen of patients with MSA-P was more clearly observed on coronal FLAIR images than on axial T2-weighted images. These findings reflected the pathological changes and might be a pathognomonic sign of MSA-P.