The proposed Rehabilitation Research and Development (RR&D) Career Development Award-2 (CDA-2) seeks to fill this gap by conducting a randomized prospective study, designed to evaluate the feasibility and efficacy of an existing web-based cognitive training program (BrainHQ; Posit Science/Brain Plasticity Institute) versus a placebo, for improving cognitive functioning and recovery outcomes. The research will be conducted iteratively, in two stages, based on the Stage Model of Behavioral Therapy Development per the National Institute on Drug Abuse, and has two overarching aims: Aim 1: Examine the acceptability, usability and feasibility of an existing web-based cognitive training program tailored for AUD and co-occurring PTSD. Aim 2: Test the efficacy of the web-based cognitive training program to improve cognitive functioning as well as clinical and functional outcomes. To test these aims, 148 Veterans with AUD and PTSD will be recruited from an outpatient Substance Use Disorder (SUD) treatment program. Participants will be randomized into either cognitive training or a computer game control. Individuals will then complete a baseline assessment, followed by 30 hours of home-based cognitive training or computer games over 6 weeks. Assessments will be completed each week of the training, as well as post-training and at post-training follow-up. The primary outcome will be performance on an (untrained) neuropsychological assessment battery 6 months post-training. Secondary outcomes include alcohol use, PTSD symptoms and quality of life.