PROJECT SUMMARY Patients with comorbid substance use (SUD) and anxiety disorders (AD) have significantly poorer health outcomes than patients with SUD alone and experience increased risk for relapse. However, less than 10% engage in treatment and only 18% of SUD facilities and 9% of mental health organizations report the capacity to provide comprehensive care. Mobile health technologies have been increasingly applied for substance use and anxiety treatments in an effort to create more comprehensive, patient centered approaches to care. Despite increasing mobile application development, the majority of existing programs are designed to target SUD or anxiety individually, few utilize evidence-based content or are clinically validated, and the majority are not designed as integrative treatment components for patients with SUD-AD. The Unwinding Anxiety (UA) mobile app can fulfill this need as it delivers digital, evidence-based psychoeducational training in a manualized, scalable, and high-fidelity manner targeting mechanistic pathways consistent with previous research. The proposed research will comprehensively assess the user experiences of UA for individuals with SUD-AD who are in recovery and explore the role of exploratory behavioral and mental health outcomes (i.e., substance use, craving, anxiety) among 48 individuals in long term recovery (>6 months). We will utilize a convergent parallel mixed methods research study design involving the collection of both quantitative and qualitative measures concurrently. We will quantitatively investigate usability, feasibility, and fidelity using the Systems Usability Scale, educational module completion, and ecological check-in usage. Qualitatively we will collect data on usability of UA within a sub-sample of participants (n=18) conducting focused interviews weekly (4 x <30 min. sessions; n=18) and 3 focus groups (k=3; n=15). Our secondary aim is to determine the degree to which UA engages exploratory outcomes specifically substance use, craving, and anxiety in preparation for future trials. Completion of this study will result in: (1) comprehensive range of customizations grounded in patients lived experience which will be used to refine one of the first mobile applications for patients with SUD-AD serving as a scalable, evidence-based adjunctive therapy; (2) provide preliminary data for a post-doctoral NIH grant application testing this customized mobile application to improve adjunctive therapies for SUD-AD treatment.