The risk of venous thromboembolism (VTE) is high for patients with brain tumors (11-20 %). Glioblastoma (GBM) patients, in particular, have the highest risk of VTE (24-30 %). The Khorana scale is the most commonly used clinical scale to evaluate the risk of VTE in cancer patients but its efficacy in patients with GBM remains unclear. The aim of this study is to estimate the frequency of VTE in GBM patients and identify potential risk factors for the development of VTE during adjuvant chemotherapy. Furthermore, we intend to examine whether the Khorana scale accurately predicts the risk of VTE in GBM patients. We retrospectively reviewed the medical records of GBM patients treated at MD Anderson during the years 2005-2011. The study cohort included 440 patients of which 64 (14.5 %) developed VTE after the start of adjuvant treatment. The median time to develop VTE was 6.5 months from the start of adjuvant treatment. On multivariate analysis male sex, BMI ≥ 35, KPS ≤ 80, history of VTE and steroid therapy were significantly associated with the development of VTE. The Khorana scale was found to be an invalid VTE predictive model in GBM patients due to poor specificity. Of the 64 patients who developed a VTE, 36 were treated with anticoagulation, 2 with an IVC filter, and 21 with both. Complications (intracranial hemorrhage, bleeding in other organs and thrombocytopenia) secondary to anticoagulation were reported in 16 % (n = 10). VTE is common in patients with GBM. Our results did not validate the Khorana scale in GBM patients. Additional studies identifying which GBM patients are at highest risk for VTE are needed to enable further evaluation of VTE preventive measures in this selected group.