Dispositional gratitude may be linked to positive mental health outcomes, yet population-based data on this association are lacking. Military veterans are an ideal population in which to examine this question given high rates of psychiatric morbidities and efforts to promote psychological resilience in this population. Data were analyzed from a nationally representative sample of 3151 U.S. veterans. Veterans were separated into three groups based on an assessment of level of dispositional gratitude: high gratitude (weighted 79.8%), moderate gratitude (9.6%), and low gratitude (10.5%). Multivariable analyses examined the associations between level of dispositional gratitude, and measures of mental health and psychosocial variables. A “dose-response” association was observed between levels of dispositional gratitude and odds of psychiatric morbidities. Higher dispositional gratitude was associated with decreased risk for lifetime history of posttraumatic stress disorder (PTSD), major depressive disorder (MDD), social phobia, nicotine dependence, and suicide attempts, and decreased risk for current PTSD, MDD, generalized anxiety disorder, and suicidal ideation (odds ratio range = 0.16–0.65). Higher dispositional gratitude was additionally associated with resilience-promoting characteristics such as optimism, curiosity, purpose in life, perceived social support, and religiosity/spirituality (Cohen’s d range = 0.11–0.73). Dispositional gratitude is prevalent in U.S. veterans, is negatively associated with psychiatric morbidities, and may help promote psychosocial factors linked to resilience in this population. Stratification of veterans with low, moderate, and high dispositional gratitude may help identify those who are at increased risk for psychiatric illness and in need of additional support.