Background: To identify early diagnostic clues, we analysed cerebrospinal fluid and serum biomarkers in patients with autoimmune glial fibrillary acidic protein astrocytopathy (GFAP‐A) and compared biomarker trends with those in patients with viral meningoencephalitis, tuberculous meningoencephalitis, and anti‐N‐methyl‐D‐aspartate receptor encephalitis. Methods: Nine GFAP‐A patients were retrospectively enrolled from the First Affiliated Hospital, Zhejiang University School of Medicine, between January 2021 and January 2022. We evaluated the clinical manifestations, laboratory findings, neuroimaging, electroencephalography, treatment and prognosis of these adult GFAP‐A cases. Cerebrospinal fluid and serum biomarker trends were compared across the GFAP‐A, viral meningoencephalitis, tuberculous meningoencephalitis and anti‐N‐methyl‐D‐aspartate receptor encephalitis groups. Results: All nine patients presented with acute or subacute onset of meningeal and/or encephalitic symptoms. Brain magnetic resonance imaging revealed lesions predominantly affecting the subcortical white matter, basal ganglia, occipital lobe, brain stem, ventricles, cerebellum and corpus callosum. Each patient achieved a modified Rankin Scale score of 0–2, and no recurrence was observed during the 6‐month follow‐up period. Conclusion: Differentiating GFAP‐A from anti‐N‐methyl‐D‐aspartate receptor encephalitis based on conventional inflammatory biomarkers remains challenging. Elevated serum C‐reactive protein and procalcitonin levels are more suggestive of viral or tuberculous meningoencephalitis. GFAP‐A is generally associated with a favourable prognosis and no recurrence within 6 months of follow‐up.