Increased oxidative and nitrosative stress are important mediators of left ventricular (LV) and vascular dysfunction in patients with chronic heart failure (CHF). This study investigated the effects of darbepoetin alfa on plasma markers of oxidative and nitrosative stress in patients with CHF with anemia. Thirty patients with CHF (LV ejection fraction [LVEF] <40%, hemoglobin <12.5 g/dl, and serum creatinine <2.5 mg/dl) were randomly assigned (1:1) to receive either a 3-month darbepoetin alfa regimen at 1.5 microg/kg every 20 days plus oral iron or placebo plus oral iron. Plasma B-type natriuretic peptide (BNP), markers of oxidative (oxidative, malondialdehyde, carbonyl proteins; antioxidative, glutathione) and nitrosative (nitrotyrosine) stress, LVEF, and 6-minute walked distance were assessed at baseline and after treatment. A significant improvement in LVEF and 6-minute walked distance was observed in only darbepoetin-treated patients. Plasma BNP (F = 14.8, p = 001), malondialdehyde (F = 9.4, p = 0.006), protein carbonyl (F = 9.2, p = 0.006), and nitrotyrosine (F = 4.4, p = 0.045) were significantly decreased, along with an increase in antioxidative glutathione (F = 4.2, p = 0.049) after darbepoetin alfa treatment. These factors were unaffected in placebo-treated patients. Darbepoetin-induced percentages of change in carbonyl protein significantly correlated with respective changes in plasma BNP (r = 0.55, p <0.05) and LVEF (r = -0.46, p <0.05). Finally, a drug-induced percentage of decrease in nitrotyrosine significantly correlated with the respective improvement in 6-minute walked distance (r = -0.63, p <0.05). In conclusion, darbepoetin alfa attenuated deleterious effects of oxidative and nitrosative stress into the cardiovascular system of anemic patients with CHF, improving also cardiac function and exercise capacity.