Abstract Objectives The study sought to assess feasibility, safety, and potential efficacy of a novel implantable extra-aortic counterpulsation system (C-Pulse) in functional class III and ambulatory functional class IV heart failure (HF) patients. Background Thirty to 40% of HF patients suffer from poor functional status and quality of life (QoL) but are not in need of end-stage treatments. We undertook a multicenter single-arm study to assess the C-Pulse System in such patients. Methods New York Heart Association (NYHA) functional class III or ambulatory functional class IV HF patients were eligible. Safety was assessed continuously through 12 months. Efficacy measurements included changes from baseline to 6 and 12 months in NYHA functional class, Minnesota Living with Heart Failure (MLWHF) and Kansas City Cardiomyopathy Questionnaire (KCCQ) scores, 6-min walk distance (6MWD), and exercise peak oxygen consumption (pVO2; 6 months only). Results Twelve men and 8 women (56.7 ± 7 years, 34 to 71 years of age) with ischemic (n = 7) or nonischemic (n = 13) cardiomyopathy were implanted. There was no 30-day mortality and no neurological events or myocardial infarctions through 12 months. At 6 months, there were 3 deaths (1 device-related). One-year survival was 85.0%. At 6 months, C-Pulse produced improvements in NYHA functional class (3.1 ± 0.3 to 1.9 ± 0.7, p = 0.0005), MLWHF (63.6 ± 19.9 to 40.2 ± 23.2, p = 0.0005), and KCCQ scores (43.6 ± 21.1 to 65.6 ± 21.5, p = 0.0002), but not 6MWD (275.5 ± 64.0 to 296.4 ± 104.9, ns) or pVO2 (14.5 ± 3.6 to 13.1 ± 4.4, ns). Improvements continued at 12 months, with 6MWD change becoming statistically significant (336.5 ± 91.8, p = 0.0425). Conclusions Use of C-Pulse in this population is feasible, appears safe, and improves functional status and QoL. A prospective, multicenter, randomized controlled trial is underway. (C-Pulse IDE Feasability Study- A Heart Assist System; NCT00815880).