Chronic obstructive pulmonary disease is characterized by low pulmonary function, inflammation, free-radical production, vascular dysfunction and subsequently a greater incidence of cardiovascular disease. By administering an acute oral antioxidant cocktail to patients with chronic obstructive pulmonary disease (n=30) and controls (n=30), we sought to determine the role of redox balance in the vascular dysfunction of these patients. Using a double blind, randomized, placebo controlled, crossover design, patients with chronic obstructive pulmonary disease and controls ingested placebo or the antioxidant cocktail (Vitamin-C, Vitamin-E, α-lipoic acid) after which brachial artery flow mediated dilation and carotid-radial pulse wave velocity were assessed using ultrasound Doppler. The patients exhibited lower baseline antioxidant levels (Vitamin-C and superoxide dismutase activity) and higher levels of oxidative stress (Thiobarbituic acid reactive species) in comparison to controls. The patients also displayed lower basal flow mediated dilation (p<0.05), which was significantly improved with antioxidant cocktail (3.1±0.5 vs. 4.7±0.6 %, p<0.05, placebo vs. antioxidant cocktail), but not controls (6.7±0.6 vs. 6.9±0.7 %, p>0.05, placebo vs. antioxidant cocktail). The antioxidant cocktail also improved pulse wave velocity in the patients (14±1 vs. 11±1 m·s−1, p<0.05, placebo vs. antioxidant cocktail), while not affecting controls (11±2 vs. 10±1 m·s−1, p>0.05, placebo vs. antioxidant). Patients with chronic obstructive pulmonary disease exhibit vascular dysfunction, likely mediated by an altered redox balance, which can be acutely mitigated by an oral antioxidant. Therefore, free radically-mediated vascular dysfunction may be an important mechanism contributing to this population’s greater risk and incidence of cardiovascular disease.