Cyclosporine A (CSA) and methotrexate (MTX) is the standard graft-versus-host disease (GVHD) prophylaxis regimen for matched sibling donor (MSD) allogeneic hematopoietic cell transplantation (allo-HCT). Recently, post-transplantation cyclophosphamide (PTCy) has been shown to be effective in GVHD prevention. In this registry-based study, we compared outcomes of 118 patients treated with PTCy and 1202 patients with CSA/MTX who underwent MSD allo-HCT for acute myelogenous leukemia. In a matched-pair analysis, PTCy was associated with a higher incidence of relapse at 2 years compared with CSA/MTX (41.1% versus 21.3%; P =.039). The incidences of day +180 grade II-IV acute GVHD and 2-year chronic GVHD were comparable in the PTCy and CSA/MTX arms (25.2% versus 25.4% [P =.90] and 42.6% versus 42.6% [P =.84], respectively). Similarly, 2-year leukemia-free survival (LFS; 54.4% versus 74.32%; P =.052), overall survival (OS; 70.6% versus 79.7%; P =.15), and GVHD-free relapse-free survival (GRFS; 38.1% versus 52.5%; P =.49) were not statistically different in the 2 arms. Our data show that GVHD prophylaxis with PTCy is feasible, resulting in similar incidences of GVHD, GRFS, LFS, and OS as seen with conventional CSA/MTX in patients undergoing allo-HCT from an MSD. The higher rate of relapse observed with PTCy needs further evaluation in a prospective study.