The maximum age of patients receiving allogeneic hematopoietic stem cell transplantation (alloHCT) has been moving up over time. However, the availability of a suitable HLA-matched sibling donor may limit access of this patient population to alloHCT. We retrospectively investigated the outcomes of umbilical cord blood transplantation (UCBT) after reduced-intensity conditioning regimens in patients aged ≥70 years with myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML) between 2010 and 2014. During this period 70 patients with AML/MDS were referred to our center for alloHCT consideration. Twenty-two patients (33%) received alloHCT: 10 UCBT, 9 HLA full-matched sibling donor transplantation, 2 haploidentical alloHCT, and 1 unrelated donor alloHCT. In UCBT, cumulative incidences of nonrelapse mortality and relapse were 20% and 30% at 2 years, respectively. The cumulative incidence of acute graft-versus-host disease (GVHD) at day +100 and chronic GVHD at 2 years was 10%. Seven patients had viral reactivation/infections. Rates of overall survival and disease-free survival were 60% and 50% at 2 years, respectively. Moreover, these outcomes seemed to be similar to that of patients aged 60 to 69 years receiving UCBT (n = 60) and patients aged ≥70 years receiving HLA full-matched sibling donor transplantation (n = 9). These results suggest that UCBT is feasible in selected AML/MDS patients aged ≥70 years. In fact, UCBT shortens the required time for an unrelated donor search and thus increases the chance of proceeding with alloHCT, which might contribute to higher rates of alloHCT in the referral group. Outcomes of UCBT are promising; however, larger studies with a longer follow-up are needed.