•NMOSD patients may encounter cognitive impairment.•It seems that vitamin B6 intake is associated with cognitive function.•Dietary B6 showed positive correlation with cognitive function in NMOSD patients. Given some evidence on the effects of vitamin B6 on cognitive function and the high prevalence of cognitive impairment in patients with Neuromyelitis Optica Spectrum Disorder (NMOSD), we conducted the present study to evaluate the correlation between dietary vitamin B6 intake and cognitive function among NMOSD patients. A cross-sectional study was designed on 24 definite NMOSD patients in Sina hospital, Tehran, Iran. A validated 168-item food frequency questionnaire was used to obtain the participants’ routine dietary habits. For the cognitive function assessment, Minimal Assessment of Cognitive Function in Multiple Sclerosis (MACFIMS) battery was administered. Vitamin B6 intake per day was calculated, and the correlation between vitamin B6 and the results of MACFIMS subtests was examined. The results revealed a positive correlation between dietary vitamin B6 intake and cognitive function in all subtests of MACFIMS. This direct correlation was significant in case of verbal and learning memory according to CVLT-II subtest (p-value:0.02; r:0.45) as well as speed of information processing and working memory according to SDMT subtest (p-value:0.04; r:0.43). The results from linear regression analysis adjusted for carbohydrate intake and disease duration indicated a significant ascending trend for the score of CVLT-II, SDMT, CVLT-II-delayed recall, and Brief Visuospatial Memory Test-Revised (BVMT-R) subtests through the quartiles of vitamin B6 intakes. Our finding indicated a positive correlation between higher dietary intake of vitamin B6 and cognitive function of NMOSD patients. Based on high prevalence of cognitive malfunction in NMOSD patients, these results are promising.