Background: Self-care behavior is important in avoiding hospitalization for patients with heart failure (HF) and refers to those activities performed with the intention of improving or restoring health and wellbeing, as well as treating or preventing disease. The purpose was to study the effects of a home-based mobile device on self-care behavior and hospitalizations in a representative HF-population. Methods and Results: SMART-HF is a randomized controlled multicenter clinical trial, where patients were randomized 1:1 to receive standard care (control group [CG]) or intervention with a home-based tool designed to enhance self-care behavior (intervention group [IG]) and followed for 240 days. The tool educates the patient about HF, monitors objective and subjective symptoms and adjusts loop diuretics. The primary outcome is self-care as measured by the European Heart Failure Self-care behavior scale and the secondary outcome is HF related in-hospital days. A total of 124 patients were recruited and 118 were included in the analyses (CG: n = 60, IG: n = 58). The mean age was 79 years, 39% were female, and 45% had an ejection fraction of less than 40%. Self-care was significantly improved in the IG compared to the CG (median (interquartile range) (21.5 [13.25; 28] vs 26 [18; 29.75], p = 0.014). Patients in the IG spent significantly less time in the hospital admitted for HF (2.2 days less, relative risk 0.48, 95% confidence interval 0.32À0.74, P = .001). Conclusions: The device significantly improved self-care behavior and reduced in-hospital days in a relevant HF population.