Background. This study evaluated the effect of continuous-flow left ventricular assist device (CF-LVAD) duration on postoperative outcomes in heart transplant patients. Methods. United Network of Organ Sharing heart transplant follow-up data from 2005 to 2015 were obtained. Patients supported by CF-LVADs who subsequently underwent cardiac transplantation were studied. The study population was divided into three groups by CF-LVAD duration of less than 1 year, 1 to 2 years, and more than 2 years. Multivariable Cox regression analysis was used to identify predictors of overall postoperative graft survival. Kaplan-Meier survival functions were used to estimate actuarial survival at 1, 2, and 5 years after transplant. The association between CF-LVAD duration and postoperative acute rejection episodes before and after hospital discharge was assessed. Results. Of 21,336 recipients, 4,382 had CF-LVADs before cardiac transplantation: 2,603 (59.4%) had CF-LVADs for less than 1 year, 1,178 (26.9%) for 1 to 2 years, and 601 (13.7%) for more than 2 years. Donor age, high body mass index, dialysis dependence, and poor functional status at transplant were significant predictors of poor posttransplant graft survival. CF-LVAD duration was associated with increased incidence of acute rejection before hospital discharge (odds ratio, 1.14; 95% confidence interval, 1.02 to 1.28; p = 0.019). Duration was not related to acute rejection episodes after discharge. There was no difference in survival among patients with increasing time durations (hazard ratio, 1.01; 95% CI, 0.89 to 1.15; p = 0.824). Graft survival at 1, 2, and 5 years among patient groups was not significantly different (p [0.824 by log-rank test) Conclusions. Duration of CF-LVAD support does not affect posttransplant graft survival. Longer duration of support increases acute rejection episodes; however, this may not translate into diminished survival. (C) 2017 by The Society of Thoracic Surgeons