We describe a 62-year-old man who developed subacute visual loss after cord blood stem cell transplantation for malignant lymphoma. Brain magnetic resonance imaging (MRI) showed bilateral hyperintense lesions in the occipital and parietal lobes. A diagnosis of progressive multifocal encephalopathy (PML) was established following brain biopsy and detection of JC virus (JCV) deoxyribonucleic acid (DNA) in the cerebrospinal fluid (CSF). He developed optic ataxia and visual inattention, and was then diagnosed as having Bálint syndrome. After he was treated with mefloquine and mirtazapine, his Bálint syndrome and, MRI findings improved and the copy number of JCV DNA in the CSF decreased. In summary, we demonstrate that patient with PML may develop Bálint syndrome and that combination therapy using mefloquine and mirtazapine may be an effective treatment. (Received August 23, 2018; Accepted November 29, 2018; Published March 1, 2019).