In 2018, the United Network for Organ Sharing implemented a change in heart allocation policy resulting in increased organ ischemia times in early analyses. This study evaluated the effect of ischemia time on 1-year mortality in the context of allocation policy changes implemented in 2006 and 2018. The United Network for Organ Sharing registry was used to identify adults undergoing heart transplantation from 2000 to 2020. Patients were stratified by the allocation policy era in which they received a transplant (2000-June 2006, July 2006-October 2018, October 2018-2020) and by ischemia time, defined as normal (≤4 hours) and prolonged (>4 hours). One-year survival was estimated using Kaplan-Meier analysis. Cox regression was used to determine risk-adjusted hazards for ischemia time on 1-year mortality. There were 40 052 patients included for analysis. Ischemia times were normal in 32 585 (81.36%) and prolonged in 7467 (18.64%) patients. The proportion of transplantations with prolonged ischemia times increased with each subsequent policy era. After the 2018 policy change, 1-year survival was 90.92% with normal ischemia times vs 87.52% with prolonged ischemia times (P < .001). Ischemia time independently predicted 1-year mortality in each era with a hazard ratio of 1.20 per hour (P = .004) in the current era. Prolonged ischemia times occur in a minority of cases but are increasing in frequency. The independent risk of prolonged ischemia time on 1-year mortality persists despite advances in storage technology and should remain a consideration in donor-recipient matching.