Military service members are at high risk for problematic substance use compared with the general population; deployment and combat exposure further increases this risk. It is thus critical to identify resiliency factors that can buffer the negative effects of military experiences and potentially prevent problematic alcohol use. The current research examines the extent to which psychological hardiness predicts lower risk of problematic alcohol use and explores potential sex differences in this association. Data are from Operation: SAFETY, an ongoing study of U.S. Army Reserve/National Guard soldiers. Negative binomial regression models examined the relation between baseline hardiness, assessed by the 15-item Dispositional Resiliency Scale, and problematic alcohol use at the 1-year follow-up, assessed by the Alcohol Use Disorders Identification Test (N = 260), controlling for baseline combat exposure (Combat Exposure subscale, Deployment Risk and Resilience Inventory-2) and baseline quantity and frequency of alcohol use. To examine the impact of hardiness on men and women, models were stratified by sex. In final, adjusted models, hardiness predicted lower risk of problematic alcohol use (adjusted risk ratio = 0.98; p < .05) for male soldiers and was unrelated to alcohol use for female soldiers (adjusted risk ratio = 1.01; p > .05). Post hoc analyses explored the impact of each dimension of hardiness (i.e., commitment, control, and challenge) on problematic alcohol use. Hardiness assessment may complement existing screening tools to identify high-risk populations; interventions to promote hardiness may help in preventing problematic alcohol use, particularly among male soldiers. (PsycInfo Database Record (c) 2021 APA, all rights reserved).