A high blood D-dimer level is often diagnosed in patients with malignant brain glioma (MBG), with 24% of these patients being detected with deep vein thrombosis of the leg and/or pulmonary embolism (PE). The cause of an elevated blood D-dimer level in most other cases remains unclear. The purpose of this study is to identify the features associated with an increased blood D-dimer level in patients after MBG resection, which may be used to improve the efficacy of adjuvant radiation therapy (ART). Results. The study included 50 patients. Three to four weeks after resection of malignant brain glioma (MBG), the blood D-dimer level was determined in patients immediately before the onset of ART. An increase in the blood D-dimer level more than by 0.25 μg/mL was detected in 78% of patients. More often, a high D-dimer level was detected in patients aged 60 years or more. In the same age group, an increase in the D-dimer level was significantly larger (p<0.05) than in younger patients (1.2 and 0.6 μg/mL, respectively). The degree of brain tumor malignancy did not affect the rate and value of an increase in the blood D-dimer level. Conclusion. Our findings indicate that an increased blood D-dimer level in patients without symptoms of venous thrombosis after craniotomy for MBG is more pronounced in patients aged 60 years and over. The degree of glioma malignancy has no significant effect on this indicator.