Background: Behavioral health treatment centers (BHTCs) rarely implement existing evidence-based practices for treating tobacco dependence, despite high rates of tobacco use among their clients. Taking Texas Tobacco Free (TTTF) has successfully targeted this disparity by delivering an evidence-based, multilevel, tobacco-free workplace program providing policy implementation and enforcement, education, provider training in tobacco screenings and treatments, and nicotine replacement therapies (NRT) to BHTCs across Texas. We describe a mixed methods design used to conduct a formative evaluation process to adapt implementation strategies to local contexts, evaluate program outcomes and characterize processes influencing program implementation in two BHTCs serving 17 clinics.Methods: Varied data collection included pre and post-implementation leader, provider, and staff surveys; and pre, mid, and post-implementation provider, staff and consumer focus groups. During implementation, data were collected via various logs (tobacco screenings, NRT delivery) to monitor program content delivery. The RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework guided translation of behavioral interventions into sustainable practice.Results: While program implementation varied between each BHTC, all clinics adopted a 100% tobacco-free workplace policy, integrated tobacco screenings into routine practice, delivered evidence-based interventions, dispensed NRT to consumers and staff, and increased provider knowledge on how to address tobacco dependence. Pre, mid, and post-implementation qualitative findings served to: 1) develop program strategies and materials adapted to local contexts and populations and address barriers; 2) adjust delivery systems of key components to enhance implementation; 3) understand reasons for success or failure to implement specific practices; and 4) reveal program integration into clinic culture, enhancing sustainability.Conclusions: Implementation of TTTF at both BHTCs increased organizational capacity in the provision of evidence-based practices to treat tobacco dependence through successfully meeting most of our RE-AIM targets. Mixing methods involved program adopters and recipients as collaborators directly shaping core interventions to their individual context and needs, thus increasing program fit, ownership, adoption and sustainability; closing the gap between research and practice. These findings contribute to the development of flexible strategies and interventions capable of addressing variable implementation contexts and barriers, thus enhancing the effectiveness and sustainability of a tobacco-free workplace program.