For patients with hematologic malignancies undergoing allogeneic hematopoietic cell transplantation, umbilical cord blood transplantation (UCBT) has become an acceptable alternative donor source in the absence of a matched sibling or unrelated donor. However, there have been few published series dedicated solely to describing the outcomes of adult patients with myelodysplastic syndrome (MDS) who have undergone UCBT. From 2004 to 2013, 176 adult MDS patients underwent UCBT as reported to the Center for International Blood and Marrow Transplant Research. Median age at the time of transplant was 56 years (range 18-73 years), with 10% having very low, 23% low, 19% intermediate, 19% high, and 13% very high-risk Revised International Prognostic Scoring System (IPSS-R) scores, respectively. The 100-day probability of Grade 2-4 acute graft-versus-host disease (GVHD) was 38%, and the 3-year probability of chronic GVHD was 28%. The probability of relapse and transplant-related mortality (TRM) at 3 years was 32% and 40%, respectively, leading to a 3-year, disease-free survival (DFS) of 28%, and overall survival (OS) of 31%. In multivariate analysis increasing IPSS-R score at time of HCT was associated with inferior TRM (P=.0056), DFS (P=.018), and OS (P=.0082), but not with GVHD or relapse. Pre-transplant comorbidities were associated with TRM (P=.001), DFS (P=.02), and OS (P=.001). Reduced conditioning intensity was associated with increased risk of relapse (RR 3.95; 95% CI 1.78-8.75, P<.001), and although a higher proportion of myeloablative UCBTs were done for those with high-risk disease, the effect of conditioning regimen intensity was the same regardless of IPSS-R score. For those who lack a matched sibling or unrelated donor, UCBT can result in long-term, disease-free survival for some patients. However, the success of UCBT in this population is hampered by a high rate of TRM.