BACKGROUNDGraft‐versus‐host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Addition of antithymocyte globulin (ATG) or post‐transplantation cyclophosphamide (PTCY) to standard immunosuppressive agents reduces GVHD in different donor settings.METHODSWe compared the outcomes of adults with acute myeloid leukemia undergoing allo‐HSCT from HLA‐identical sibling donors after the use of PTCY (n = 197) or ATG (n = 1913).RESULTSPatients in the PTCY group were younger than those in the ATG group (median age, 47 vs 54 years; P < .01). Peripheral blood was the most frequently used stem cell source, being significantly more frequent in the ATG group than in the PTCY group (95% vs 70% P < .01). The conditioning regimen was more frequently myeloablative in the PTCY group than in the ATG group (59% vs 48%; P < .01). Time to neutrophil engraftment was shorter in the ATG group than in the PTCY group (17 vs 20 days; P < .01). No differences were observed according to the other transplantation outcomes, except for chronic GVHD of all grades and extensive chronic GVHD at 2 years, which were significantly lower in the ATG group compared with the PTCY group (P < .02).CONCLUSIONPTCY is feasible in an HLA‐identical sibling setting, and despite similar outcomes, ATG may be associated with lower incidence of chronic GVHD.