Abstract: Introduction: Understanding the incidence and predictors of postpartum depression (PPD) among active-duty service members is critical given the importance of this population and its unique stressors. Methods: We conducted a retrospective cohort study of all active-duty U.S. Army soldiers with a record of at least one live-birth delivery between January 2012 and December 2013. Multivariate logistic regression models were used to estimate associations between demographic, health-related, and military-specific variables and diagnoses of PPD in the total population (N = 4,178) as well as in a subpopulation without a record of depression before delivery (N = 3,615). Results: The overall incidence of PPD diagnoses was 15.9% (N = 664 cases) among the total population and 10.4% (N = 376 cases) among those without prior depression. Statistically significant predictors of PPD in the adjusted model included lower pay grade, a higher number of prior deployments, a higher number of child dependents, tobacco use, and a history of depression or anxiety before or during pregnancy. For soldiers without a history of depression, lower pay grade, and a history of anxiety before or during pregnancy were significantly associated with PPD. Conclusions: Knowing the predictors of overall and novel onset PPD diagnoses in this population could help establish clearer guidelines on PPD prevention, screening, management, and return to duty.