Background: O6-methylguanine-DNA methyltransferase (MGMT) is a DNA-repair enzyme that correlates with tumor resistance mechanism to chemotherapy. Methylation of the MGMT promoter inhibits the cells from producing MGMT and is useful to predict chemotherapy’s effectiveness with alkylating agents. This study aims to evaluate the MGMT promoter methylation of low-grade and high-grade glioma in the Neurosurgery Department of Cipto Mangunkusumo National General Hospital. Methods: We evaluated MGMT promoter methylation status using methylation-specific polymerase chain reaction in low and high-grade glioma patients who underwent surgical resection in the Neurosurgery Department of Cipto Mangunkusomo Hospital Jakarta. The result then correlated with age, sex, Karnofsky Performance Scale (KPS), and glioma grading. Data were analyzed using SPSS version 20 for Windows. Results: MGMT promoter methylation was observed more often in patients diagnosed with age more than 40 years old than in patients less than 40 years old (85.7% vs. 50.0%), also more in men than women (77.7% vs. 50.0%). In patients with KPS more than 70 and KPS 70 or less, methylation of MGMT promoter was observed in 70.0% and 57.1%, respectively. Based on tumor grading, MGMT promoter methylation was observed more often in low-grade gliomas (WHO grade II) than high-grade gliomas (WHO grade II and IV) (85.7% vs. 50.0%). There was no significant relationship between gender, age, KPS, malignancy degree, and Overall Survival (OS) to the MGMT promoter methylation (p>0.05). Conclusion: MGMT promoter methylation was observed less in the higher grade of tumors (grade IV), lower KPS, younger age at the time of diagnosis, and female patients, although the differences were not statistically significant. MGMT promoter methylation was observed more often in gliomas with oligodendroglioma components. © 2021, Sanglah General Hospital. All rights reserved.