In the present systematic review, we summarize the feasibility, usability, efficacy, and effectiveness of mental health-related apps created by the Veterans Affairs (VA) or the Department of Defense (DoD). Twenty-two articles were identified, reporting on 8 of the 20 VA/DoD mental health self-management and treatment companion apps. Review inclusion criteria were studies that reported original data on the usability, acceptability, feasibility, efficacy, and effectiveness, or attitudes toward the app. We collected data from each article regarding type of study, sample size, participant population, follow-up period, measures/assessments, and summary of findings. The apps have been tested with patients seeking treatment, patients with elevated mental health symptoms, and clinicians. The strongest area of support for the apps is regarding evidence of their feasibility and acceptability. Research support for efficacy and effectiveness of the apps is scarce with exceptions for two apps (PTSD Coach, Virtual Hope Box). Until more evidence accumulates, clinicians should use their judgment and be careful not to overstate the potential benefits of the apps. (PsycINFO Database Record (c) 2019 APA, all rights reserved).