Background: Neuromedin B (NMB) is a neuropeptide that plays a key role in many physiological processes and is involved in the pathology of various diseases. Increased levels of NMB have been reported in solid tumors. Therefore, we investigated the prognostic value of NMB in glioblastoma (GBM). Methods: Expression profiles of NMB mRNA were investigated in GBM and normal tissues using data from the cancer genome atlas (TCGA). NMB protein expression was obtained using data from the Human Protein Atlas. Receiver operating characteristic (ROC) curves were evaluated in GBM and normal tissues. The survival effect of NMB in GBM patients was evaluated using the Kaplan-Meier method. Protein-protein interaction networks were constructed using STRING, and the functional enrichment analyses were performed. The relationship between NMB expression and tumor-infiltrating lymphocytes was analyzed using the Tumor Immune Estimation Resource (TIMER) and the Tumor-Immune System Interaction database (TISIDB). Results: NMB was overexpressed in GBM relative to normal biopsy specimens. The ROC analysis showed that the sensitivity and specificity of NMB in GBM were 96.4% and 96.2%, respectively. Kaplan-Meier survival analysis showed that GBM patients with high NMB expression had a better prognosis than those with low NMB expression (16.3 vs. 12.7 months, p = 0.002). Correlation analysis showed that NMB expression was associated with tumor-infiltrating lymphocytes and tumor purity. Conclusions: High expression of NMB was associated with increased GBM patient survival. Our study indicated that the NMB expression may be a biomarker for prognosis and that NMB may be an immunotherapy target in GBM.