It remains unclear how specific innovations in allogeneic hematopoietic cell transplantation (HCT) attained over the past decades have contributed to improvement in transplantation outcomes. To address this question, we conducted a registry-based study of adults with acute myeloid leukemia in first or second complete remission who underwent allogeneic HCT between 1994 and 2013 from a sibling (N = 1600) or unrelated (N = 2113) donor matched at the antigen level for HLA-A, -B, and -DR. Preliminary analysis led us to focus on comparisons between the 1994-2006 and 2007-2013 periods. Significant improvement in survival was observed in the later cohort compared to the earlier cohort for unrelated HCT (P = 0.004), but not for related HCT (P = 0.767). The improvement in unrelated HCT was solely due to diminished non-relapse mortality (P = 0.001), while incidence of relapse did not change over time (P = 0.934). The percentage of patients receiving transplants from 8/8-matched unrelated donors was significantly higher in the later cohort (P < 0.001), and their survival was significantly better than that of those undergoing mismatched unrelated HCT (P = 0.022). These findings suggest that advances in HLA-typing technology have been vital for improvement in transplantation outcomes.