Objectives Alcohol use disorders (AUDs) are associated with significant physical and mental health concerns. Interventions focused on increasing physical activity (PA) in this population may improve overall physical and mental health associated with AUDs. Given how ubiquitous smartphones have become, PA apps may be a feasible, acceptable, and potentially scalable approach to integrating PA in alcohol recovery. To date, there are no PA apps targeted specifically for this population. Design The current study describes 2 formative phases in the development of Fit&Sober, a theory-informed smartphone app designed to increase PA in patients with alcohol dependence. Methods Phase 1 consisted of questionnaires and focus groups (3 groups with total N = 23) conducted with patients in current AUD treatment regarding their preferences and feedback on the proposed app design and components. Phase 2 consisted of individual usability sessions (N = 10) conducted with a different set of patients with AUD, in which feedback was provided on the look, usability, and functionality of the Fit&Sober app prototype. Results Phase 1 evaluated key components of a physical activity app designed especially for increasing PA in early recovery and refined app features such as the logo, graphical display of data, and specific physical activity-relevant affect words to be used in the app. Phase 2 usability studies provided support for usability, attractiveness, and potential usefulness in the target population. Conclusions Through the iterative 2-phase process, a prototype of the Fit&Sober app was created and readied for pilot testing in patients with AUD.