Several studies provided evidence of a consistent antileukemic effect induced by cytomegalovirus (CMV) replication in acute myeloid leukemia (AML) patients receiving allogeneic hematopoietic stem cell transplantation (HSCT), however the use of antithymocyte globulin (ATG) as graft‐versus‐host disease prophylaxis, may potentially abrogate the protective effect of CMV infection. To address this issue, we retrospectively analyzed the risk of relapse in a cohort of 101 patients with AML who received grafts from an unrelated donor after a conditioning regimen including ATG. The cumulative incidence of CMV reactivation, evaluated by RT qPCR, was 59% at 12 months, and 93% of CMV reactivations occurred within the first 100 days post HSCT. The 5‐year cumulative incidence of relapse in patients with CMV reactivation was 29% compared with 37% for patients without CMV reactivation, and the only factor associated with a reduced 5‐year cumulative incidence of relapse was the disease status at HSCT (P < 0.001). In the multivariable model adverse cytogenetics (HR 2.42, 95% CI 1.02‐5.72; P = 0.044) and acute GVHD (HR 3.36, 95% CI 1.32‐8.54; P =  0.011) were independent risk factors for reducing overall survival (OS), while the presence of chronic GVHD was associated with a better OS (HR 0.37, 95% CI 0.15‐0.89; P = 0.027). CMV replication was not an independent risk factor for OS (HR 1.06, 95% CI 0.07‐15.75; P = 0.965). In Conclusion, the results of present study suggest that relapse prevention in patients with AML receiving T‐cell depleted HSCT using ATG do not benefit from CMV reactivation. Am. J. Hematol. 90:E117–E121, 2015. © 2015 Wiley Periodicals, Inc.