BACKGROUND: Military veterans living with post-traumatic stress disorder (PTSD) face significant physical and functional health disparities, which are often aggravated over time and in the context aging. Evidence has shown that physical activity can positively impact age-related health conditions, yet exercise trials in older adults with mental disorders are rare. Our study was a tailored and targeted pilot exercise intervention for older veterans with PTSD. METHODS: Fifty-four older veterans with PTSD (mean age = 67.4 years, 90.7% male, 85.2% non-white) were randomized to supervised exercise (n = 38) or wait-list usual care (n = 18) for 12 weeks. Physical activity (MET-min/wk) and aerobic endurance (assessed with the 6-minute walk test) were primary outcomes. Secondary outcomes were physical performance (strength, mobility, balance), cardiometabolic risk factors (eg, waist circumference), and health-related quality of life. RESULTS: At 12 weeks, a large effect of the intervention on physical activity levels (Cohen's d = 1.37) was observed compared to wait-list usual care. Aerobic endurance improved by 69 m in the exercise group compared to 10 m in wait-list group, reflecting a moderate between-group effect (Cohen's d = 0.50). Between-group differences on 12-week changes in physical performance, cardiometabolic risk factors, and health-related quality of life ranged from small to large effects (Cohen's d = 0.28-1.48), favoring the exercise arm. CONCLUSION: Participation in supervised exercise improved aerobic endurance, physical performance, and health-related clinical factors in older veterans with PTSD; a medically complex population with multiple morbidity. Group exercise is a low-cost, low-stigma intervention, and implementation efforts among older veterans with PTSD warrants further consideration.