We examined the influence of positive psychological capital (PsyCap), a metaconstruct that combines established psychological predispositions to be resilient to stress, on the well-being of soldiers during combat deployment. Among U.S. Army personnel deployed in Iraq, cognitive appraisal of stress mediated the effects of trait PsyCap on health symptoms. The indirect effects through appraisal were moderated by levels of exposure to potentially traumatic stimuli. Trait PsyCap covaried more strongly with cognitive appraisals, and had stronger indirect effects through appraisal on health, among soldiers in units with higher levels of potentially traumatic exposures. We discuss implications for research on resilience to trauma in the workplace and for helping workers cope with potentially traumatic exposures.