This study aimed to identify the prevalence, clinical and radiographic characteristics, and risk factors for cognitive dysfunction in patients with Neuromyelitis optica spectrum disorder (NMOSD). Eighty-three participants who were diagnosed with NMOSD were recruited. Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA) and Frontal Assessment Battery (FAB). The mean age of the patients was 47.78 ± 13.14years, with an average of 12.05 ± 4.62years of formal education. The majority (54%) exhibited cognitive impairment, defined by a MoCA score < 25 (mean: 22.96 ± 3.82). Disease severity (evaluated by the Expanded Disability Status Scale) and lower formal education levels were associated with cognitive impairment (p = 0.011 and < 0.001, respectively). The annualized relapse rate, disease duration, and AQP4 antibody status were not associated with cognitive impairment. Interestingly, informant-reported cognitive decline was associated with poorer cognitive performance (p = 0.027). Radiographic findings of lesion location and severity were associated with MoCA-assessed cognitive performance, particularly for lesions in the right parietal lobes (p = 0.023). Hippocampal atrophy was negatively correlated with FAB scores. In conclusion, approximately half of the Thai patients with NMOSD exhibited cognitive impairment, which was associated with age, formal education level, disease severity, relative perception, and specific radiological findings. Further studies incorporating comprehensive neuropsychological tests and subjective cognitive complaints are warranted.