The aims of this pilot study were to investigate the levels of biomarkers of microglial/macrophage activation—YKL‐40, sCD163, and sCD14—in patients with neuromyelitis optica spectrum disorder (NMOSD) and determine the possible associations between these biomarkers and Expanded Disability Status Scale (EDSS) scores. Here, CHI3L1 is linked to neuromyelitis optica.