Heart failure (HF) affects nearly 6 million Americans and leads to significant impairments in functioning, quality of life, and survival. Health behaviors (e.g., physical activity, low-sodium diet, medications) are associated with improved health, including survival, in HF, but most HF patients do not adhere adequately to these behaviors. Existing health behavior programs have had limited impact on adherence and cardiac outcomes, are inaccessible to many patients, and do not target psychological factors independently associated with heart health. Motivational interviewing- (MI-) based programs have been shown to increase engagement in HF self-care behaviors but may not be sufficient to improve downstream health outcomes in HF patients. Positive psychology (PP), which utilizes systematic activities (e.g., using strengths, expressing gratitude) to cultivate well-being, may be an important component of a health behavior program in HF. Positive psychological constructs are prospectively and independently associated with both health behavior adherence and improved cardiovascular health, and PP interventions have been shown to improve these constructs and increase health behavior adherence in patients with or at risk for cardiovascular disease. Furthermore, PP could be combined with MI to promote self-efficacy, motivation, and intention to engage in health behaviors. We recently completed a multi-stage project (REACH for Health) to develop a 12-week, telephone- delivered, combined positive psychology-motivational interviewing (PP-MI) intervention to promote physical activity, diet, and medication adherence in HF. We now aim to examine the efficacy of this program, with additional twice weekly PP and health behavior text messages for a total of 24 weeks, compared to an MI- based educational control condition, in an NIH Stage II, randomized clinical trial in 280 patients with New York Heart Association class I-III HF and suboptimal adherence to physical activity, diet, or medications. The primary study outcome will be change in objectively measured health behavior adherence (composite outcome of moderate to vigorous physical activity [measured via accelerometer], sodium intake [24h urinary sodium], and medication adherence [Medication Event Monitoring System electronic pill bottle]), and we hypothesize that PP-MI will lead to greater improvements in adherence compared to the MI-based educational condition. We also will measure the intervention’s impact on psychological health, quality of life, functional outcomes, markers of cardiovascular health (e.g., body mass index, lipids, glucose), and major adverse cardiac events. We will utilize our team’s expertise in clinical trials, cardiology, and PP- and MI-based interventions to effectively and efficiently perform the proposed trial, which—consistent with the goals of PA-18-722—aims to “test [an] innovative approach…for maintaining individuals’…adherence to complex health care regimens.” If effective, we...