Older adults with B-cell acute lymphoblastic leukemia (B-ALL) have poor survival. We examined the effectiveness of reduced intensity conditioning (RIC) hematopoietic cell transplant (HCT) in adults with B-ALL age 55 years and older and explored prognostic factors associated with long-term outcomes. Using CIBMTR registry data, we evaluated 273 patients (median age 61, range 55-72) with B-ALL with disease status in CR1 (71%), >CR2 (17%) and Primary Induction Failure (PIF)/Relapse (11%), who underwent RIC HCT between 2001 and 2012 using mostly unrelated donor (59%) or HLA-matched sibling (32%). Among patients with available cytogenetic data, the Philadelphia chromosome (Ph+) was present in 50%. The 3-year cumulative incidences of nonrelapse mortality (NRM) and relapse were 25% (95% confidence intervals (CI): 20-31%) and 47% (95% CI: 41-53%), respectively. Three-year overall survival (OS) was 38% (95% CI: 33-44%). Relapse remained the leading cause of death accounting for 49% of all deaths. In univariate analysis, 3 year risk of NRM was significantly higher with reduced Karnofsky performance status (KPS <90: 34% (95% CI: 25-43%) versus KPS ≥90 (18%; 95% CI: 12-24%, P = 0.006). Mortality was increased in older adults (66+ vs. 55-60: Relative Risk [RR] 1.51 95% CI: 1.00-2.29, P = 0.05) and those with advanced disease (RR 2.13; 95% CI: 1.36-3.34, P = 0.001). Survival of patients in CR1 yields 45% (95% CI: 38-52%) at 3 years and no relapse occurred after 2 years. We report promising OS and acceptable NRM using RIC HCT in older patients with B-ALL. Disease status in CR1 and good performance status are associated with improved outcomes. Am. J. Hematol. 92:42-49, 2017. © 2016 Wiley Periodicals, Inc.