The aim of this report was to examine the safety of physical therapy for hemiplegia in a patient with neuromyelitis optica in the acute phase. A 32-year-old female with neuromyelitis optica diagnosed by magnetic resonance imaging had a T2-weighted hyperintense lesion in the central cord from C2 to T2 and was positive for serum anti-aquaporin-4 antibodies. Upon admission to the hospital, her Expanded Disability Status Scale, Medical Research Council scale for muscle strength score, and sensory score (according to the American Spinal Injury Association sensory assessment) were 9.0, 37, and 158, respectively. The patient commenced physical therapy on day 4. A locomotion exercise using an orthosis was started as soon as possible. Her left-side limb muscle strength improved to approximately grade 4 by a manual muscle test with improvements in the Expanded Disability Status Scale score (from 9.0 to 6.0), Medical Research Council scale for muscle strength score (from 37 to 54), sensory score (from 152 to 203), and all functional independence measure dominants compared with the respective values on admission. This report shows that a carefully supervised physical therapy program did not cause deterioration of the patient's symptoms.