Chronic alcohol abuse increases lung oxidative stress and susceptibility to respiratory infections by impairing alveolar macrophage (AM) function. NADPH oxidases (Nox) are major sources of reactive oxygen species (ROS) in AMs. We hypothesized that treatment with the critical antioxidant glutathione (GSH) attenuates chronic alcohol-induced oxidative stress, by down-regulating Noxes, and restores AM phagocytic function. Bronchoalveolar lavage (BAL) fluid and AMs were isolated from male C57BL/6J mice (8-10 weeks) treated ± ethanol in drinking water (20% w/v, 12 weeks) ± orally gavaged GSH in methylcellulose vehicle (300 mg/kg/day, during week 12). MH-S cells, a mouse AM cell line, were treated ± ethanol (0.08%, 3 d) ± GSH (500 μM, 3 d or last 1 d of ethanol). BAL and AMs were also isolated from ethanol-fed and control mice ± inoculated airway Klebsiella pneumoniae (200 CFUs, 28 hours) ± orally gavaged GSH (300 mg/kg, 24 hours). GSH levels (HPLC), Nox mRNA (qRT-PCR) and protein levels (western blot and immunostaining), oxidative stress (DCFH-DA and Amplex Red), and phagocytosis (S. aureus internalization) were measured. Chronic alcohol decreased GSH levels, increased Nox expression and activity, enhanced oxidative stress, impaired phagocytic function in AMs in vivo and in vitro, and exacerbated K. pneumonia-induced oxidative stress. Although how oral GSH restored GSH pools in ethanol-fed mice is unknown, oral GSH treatments abrogated the detrimental effects of chronic alcohol exposure and improved AM function. These studies provide GSH as a novel therapeutic approach for attenuating alcohol-induced derangements in AM Nox expression, oxidative stress, dysfunction, and risk for pneumonia.