Travelers’ diarrhea (TD) has historically been a common illness among visitors to developing nations. Although recent studies indicate decreasing incidence of TD among short-term travelers, a systematic review of illness among long-term travelers, including deployed military personnel, has not been conducted in more than 10 years. We conducted a literature search of studies published between 2005 and 2015 that evaluated TD in populations of deployed military personnel or similar long-term travelers (travel ≥1 month) to developing nations. Our literature search identified 28 studies for inclusion. We found that the incidence of TD remained high (10% clinical incidence, 30% self-reported incidence), with variability depending on region of travel and similar rates in both military and civilian long-term travelers. Bacteria (Escherichia coli, Campylobacter, Shigella, and Salmonella species) were the most commonly identified enteropathogens. Fifty percent of affected individuals experienced lost ability to work and 5% required hospitalization. This systematic review demonstrates that among deployed military personnel and longterm travelers, TD remains a prevalent disease that can significantly impact individual readiness for duty. These data demonstrate that to maintain operational readiness among deployed personnel, a focus on vigilance for disease and early treatment of cases is vital.