PROJECT SUMMARY/ABSTRACT Cardiovascular disease (CVD) is the leading cause of death and a substantial source of morbidity for adults ≥ 65 years old. Cardiac rehabilitation (CR) is a secondary prevention strategy proven to reduce death and recurrent CVD events, as well as improve physiological and psychological functioning. Veterans constitute a unique patient population with complex, elevated CVD risk profiles that could significantly benefit from CR. Frequently cited barriers for veteran participation in traditional, center-based CR programs are rooted in social and economic drivers of health disparities, such as geographic distance to CR centers, transportation limitations, and patient priorization. Technology-enhanced CR (TECR), an adapted home-based CR program with technological supplements (e.g., video-enabled visits, remote heart monitoring, fitness trackers) has been promoted as a potential solution. TECR has seen early success with engaging VA patients but presents new challenges for older adults. However, aging-related challenges that must be considered include physical and cognitive limitations, reduced programmatic social support for behavior change, and anxiety and frustration with learning and operating new technologies. Evaluations of TECR interventions among older veterans is limited, and COVID-19 operational restrictions and safety protections underscore the urgency for understanding alternative CR strategies for vulnerable populations. This project will build on an existing pragmatic trial evaluating CR in a veteran population and employ a mixed-methods sequential design to examine intersectional determinants of TECR participation. Using a multi-ecological, theory-driven framework, the project seeks to achieve three aims. The first aim will identify contextual, interpersonal, and individual-level predictors of enrollment for older veterans in a TECR program using secondary data from the parent study. Similarly, the second aim involves a secondary analysis to identify multilevel correlates of active engagement among veterans who enroll in TECR. Building on the results of the first two aims, a two-stage qualitative study will be conducted to a) examine TECR perceived ease of use, perceived usefulness, and attitudes towards TECR among eligible veterans who select or decline TECR enrollment; and b) examine barriers and facilitators of engagement for older adults enrolled in TECR. The proposed research is timely and directly aligns with the strategic directions for the National Institute on Aging. By using a theory-based framework to evaluate TECR participation, this study will identify strengths and opportunities for increasing enrollment and adherence to an effective CVD behavior change intervention. Understanding how these factors work mechanistically is crucial for increasing CR uptake and reducing health disparities for older veterans.