This research partnership between the D&T and BSD Divisions will extend and enhance an ongoing successful cross-center collaboration in a high priority topic for the larger Center. The purpose of this proposal is to conduct a pilot evaluation of the VetChange mobile app in order to test its feasibility, acceptability, and potential efficacy to reduce alcohol consumption, PTSD severity, and improve psychosocial functioning among Veterans with PTSD who exhibit signs of problem drinking. In this study, 280 Veterans with problem drinking and clinically significant PTSD symptoms will be recruited using social media and randomized in equal numbers to receive one of four conditions: 1) Assessment only, 2) VetChange mobile app only, 3) AFT plus the VetChange mobile app supplemented with a package of supportive accountability tools (VetChange+). In addition to receiving the mobile app, VetChange+ participants will receive SMS reminders to log drinking behavior using the mobile app. The investigators will track objective use of the VetChange mobile app to assess feasibility, and this usage data will also be used in real-time to tailor the content of text messages provided to participants in the VetChange+ condition. Participants will complete measures of alcohol use, functional well-being, and PTSD symptoms at baseline and again after 8 weeks (posttreatment). At post-treatment, participants in the VetChange app arms of the study will also be asked to report their level of satisfaction with the app and to complete a brief qualitative evaluation of their experience using the VetChange mobile app.