This study examined the impact of prednisone (PDN) on cytomegalovirus (CMV) infection after allogeneic stem cell transplantation (allo-SCT) according to donor and recipient CMV serostatus. Seventy-five patients underwent allo-SCT from June 2010 to July 2012. The risk of CMV infection according to donor and recipient serostatus was defined as follows: high risk (HR; D–/R+), intermediate risk (IR; D+/R+ and D+/R–), and low risk (D–/R–). Forty-five patients (60%) developed CMV infection, and 46 patients (61%) received steroids (PDN ≥ 1 mg/kg/day) to treat acute graft-versus-host disease. CMV infection was more common in those treated with steroids than in those not treated with steroids (70% versus 44%, respectively, P < .05). Overall, 40% of patients had recurrent CMV infection (50% PDN versus 24% no PDN, P < .05). Steroids had no impact on the incidence of CMV infection or its recurrence in HR patients; however, steroids did prolong the need for antiviral treatment. The incidence of CMV infection in IR patients was higher in those receiving PDN (80% PDN versus 41% no PDN, P = .01); recurrence rates were also higher (55% PDN versus 18% no PDN, P = .02). We analyzed CMV-specific immune reconstitution in the first 22 patients of the series and observed that patients on steroids had lower levels of CMV-specific lymphocytes TCD8 (P < .05 on days +60, +100, and +180) and that CMV-specific immune reconstitution (defined as lymphocytes CD8/IFN ≥ 1 cell/µL) was achieved later (after day +100 post-SCT) in the steroid group.