BACKGROUND: In the absence of matched related and unrelated donors, an alternative donor has to be found for patients in need of allogeneic hematopoietic cell transplantation (HCT). There are at least three donor options: a mismatched unrelated donor (MMUD), an umbilical cord blood (UCB), and a haploidentical related donor (Haplo); however, the optimal alternative donor selection remains to be established. OBJECTIVES: This study aimed to address how the outcomes of these three alternative donor transplantations differ, and whether the outcomes of each of the alternative donor transplantations have changed over time. STUDY DESIGN: We retrospectively analyzed Japanese nationwide transplantation registry data of adults with acute myeloid leukemia (AML) undergoing allogeneic HCT during first complete remission (CR) from MMUD with a 7/8-match at the allele level (n = 601), UCB, (n = 1110), or Haplo (n = 221) between 2007 and 2018. RESULTS: For patients transplanted from 2007 to 2014, the 3-year overall survival (OS) for the MMUD, UCB, and Haplo groups was 60%, 54%, and 47%, respectively (P = 0.022). For those transplanted from 2015 to 2018, the 3-year OS was 60%, 66%, and 63%, respectively (P = 0.693). Multivariate analysis revealed that the risks of both overall mortality and non-relapse mortality (NRM) were significantly lower in the later period than in the earlier period in the UCB group [hazard ratio (HR), 0.66; P < 0.001 for OS; and HR, 0.64; P < 0.001 for NRM], and in the Haplo group (HR, 0.58; P = 0.019 for OS; HR, 0.39; P = 0.004 for NRM), but not in the MMUD group (HR, 1.07; P = 0.631 for OS; HR, 1.26; P = 0.175 for NRM). The results of a test for interaction showed a significant difference in the effect of the transplantation period on OS and NRM between the MMUD and UCB groups (P = 0.014 for OS and P = 0.004 for NRM) and between the MMUD and Haplo groups (P = 0.034 for OS and P = 0.003 for NRM). CONCLUSION: These findings demonstrate the recent improvements in the outcomes of UCB and Haplo transplantations in patients with AML in first CR, consequently resulting in the similar OS of patients transplanted from MMUD, UCB, and Haplo in the later period.