Background: Many peripheral blood biomarkers are associated with glioma grade, but eosinophils (Eo) are scarcely reported. This study assessed preoperative peripheral eosinophil levels and other peripheral biomarkers presented in prior literature, probing their associations and diagnostic value in the grading of glioma, including its most aggressive type, glioblastoma (GBM). Methods: Patients newly diagnosed with neuroepithelial tumors were included and divided into low-grade glioma (LGG)/high-grade glioma (HGG) groups and non-GBM/GBM groups separately. Preoperative peripheral biomarkers were collected, such as the counts of Eo, neutrophils (Neu), and lymphocytes (Ly), and values such as the eosinophil to lymphocyte ratio (ELR) and neutrophil to lymphocyte ratio (NLR) were calculated. Correlation analyses were also performed between these biomarkers and the groups. Receiver operating characteristic curves were utilized to assess the individual and joint diagnostic values of the biomarkers. Results: The HGG patients presented lower Eo and ELR values, which had negative correlations with glioma grade. The diagnostic efficiency of Eo and ELR could be enhanced when combined other biomarkers. In the non-GBM vs GBM analysis, GBM patients displayed reduced Eo and a negative correlation between Eo and a GBM diagnosis The combination of Eo and other biomarkers enhanced the diagnostic efficiency. Conclusions: A negative correlation between peripheral eosinophils and glioma grade was found in our study. Numerous cytokines derived from eosinophils could regulate the immune response and affect the tumor microenvironment; moreover, eosinophils may inhibit the tumorigenesis of glioma, which should be explored in the future and may enlighten some new paths for glioma therapy. © 2019 The Author(s).