Background: Glioblastoma is the most common adult malignant glioma, with poor prognosis and adverse neurological sequelae. Physical activity improves outcomes in patients with other cancers, but has not been evaluated in GBM. This prospective, single-arm intervention trial examines feasibility and preliminary efficacy of exercise on PFS, cognition and QOL in newly diagnosed GBM patients. Method: Participants are English-speaking GBM patients scheduled for concurrent chemoradiation at PMH, 18-65 years old, ECOG ≤ 2. The 3-month home-based exercise program includes aerobic and resistance training, tailored to prior fitness level, current physical status, and individual interests. Assessments of physical and neurocognitive functions, mood, fatigue, sleep, and QOL, occur within 2 weeks of starting chemoradiation, and approximately 3, 6, 12, and 18 months later, or until tumor progression. Feasibility will be assessed by accrual, retention, and adherence rates. Outcomes include PFS (RANO criteria), change in cognition (reliable change index method), physical activity and sleep (actigraphy, self-report questionnaires). Time-to-event outcomes will be estimated (Kaplan-Meier), and mixed modelling will explore individual and disease variables that contribute to outcomes. Results: During the first five months of recruitment, 13 of 19 eligible patients consented. Nine completed the exercise program. One patient died after the intervention and none of the others progressed. No exercise-related serious adverse events occurred. Preliminary results will be presented at the meeting. Discussion: Exercise appears feasible for GBM patients. Effects on survival, performance status, cognition, sleep, mood, and QOL are ongoing. Results may guide physical activity recommendations in GBM and generate avenues for translational research.