Mental health disorders have historically accounted for significant morbidity, health care utilization, disability, and attrition from military service. From 2016 through 2020, a total of 456,293 active component service members were diagnosed with at least 1 mental health disorder and 84,815 were diagnosed with mental health problems related to family/support group problems, maltreatment, lifestyle problems, substance abuse counseling, or social environment problems. Crude annual incidence rates of at least 1 mental health disorder decreased between 2016 and 2018, then increased in 2019 and decreased again in 2020. Most of the incident mental health disorder diagnoses were attributable to adjustment disorders, anxiety disorders, depressive disorders, “other” mental health disorders, alcohol-related disorders, and post-traumatic stress disorder. Similar to the last MSMR update, rates of incident mental health disorders were generally higher among female service members and Army members and declined with increasing age. Ongoing efforts to assist and treat service members should continue to promote help-seeking behavior to improve the psychological and emotional well-being of service members and reduce the burden of mental health disorders.