Purpose: Behavioral health (BH) disorders can impact Service Members’ ability to perform or even remain in service. The purpose of this analysis is to assess the burden of BH disorders on the Military Health System and identify demographic and military characteristics associated with BH diagnosis in active-duty (AD) U.S. Army Soldiers during 2016–2020. Method: This retrospective analysis used medical encounter data from the Military Health System Data Repository to identify Soldiers with BH diagnoses, which were defined as encounters with BH International Classification of Diseases, 10th edition F-code series in the first diagnostic position. Demographic and military characteristics for each Soldier were extracted from Defense Manpower Data Center data. Logistic regression was used to estimate the associations between each covariate of interest and BH diagnoses. Trends in the annual prevalence of BH disorder diagnosis over time were assessed using linear regression. Annual and 5-year prevalence of BH diagnoses, beta estimates and p values, and crude and adjusted odds ratio with 95% confidence were stratified and reported by sex. Results: Over the entire period, 29% of men and 40% of women were diagnosed with a BH disorder. Annual prevalence of any BH diagnosis showed a statistically significant downward trend across the 5-year period for men and women. Adjustment disorder had the highest prevalence among both men and women. Prevalence increased with age: from 23% of men and 34% of women aged 17–24 years to 41% of men and 53% of women 45–64 years of age. Senior enlisted Soldiers (E7–E9) had more than double the odds of BH diagnosis compared with commissioned officers (O1–O10). Black or American Indian or Alaska Native Soldiers had the highest odds of BH diagnosis compared to Asian or Pacific Islander Soldiers. Soldiers who were currently or formerly married (i.e., divorced or widowed) had higher odds of BH diagnosis than single (never married) Soldiers. Conclusion: The prevalence of BH disorders diagnosed in the AD Army was similar to that in other Services, but lower than in the civilian population. Differences by sex and race followed patterns in the civilian population, but age and marital status did not. Recommendations focus on the contextual factors and personal behaviors that contribute to the risk of some disorders. A marketing approach targeting new Soldiers might emphasize early identification and mitigation of behaviors that could derail their career. Interviewing senior leaders with BH disorders may reveal protective factors and positive behaviors that have enabled them to succeed in their military careers.