This study estimates the relationship between combat exposure and several risky health behaviors: cigarette consumption, binge drinking, and drug use. We find that the U.S. active duty military personnel deployed to combat zones with enemy firefight are more likely to subsequently smoke cigarettes, consume alcohol, and use illicit drugs than their counterparts deployed to noncombat operations. Our results suggest that the mental health effects of combat can explain up to two‐thirds of the estimated association between combat exposure and risky health behaviors. (JEL H56, I12)