Latent infection with human cytomegalovirus (CMV) is common. Functional immunity effectively contains such latent infections; however, CMV reactivation may cause significant complications in patients undergoing allogeneic hematopoietic cell transplantation (alloHCT). In spite of the universal implementation of post-transplant screening for CMV viremia and the institution of pre-emptive antiviral management, CMV disease still occurs in a small portion of patients. Moreover, interactions between CMV and the immune system have significant implications for the incidence of graft-versus-host disease, the recurrence of malignancy, and non-relapse mortality following alloHCT, even in the era of pre-emptive antiviral management. CMV serostatus thus remains an important consideration for patients undergoing alloHCT. We review the clinical impact of CMV in the setting of alloHCT, interactions between CMV serostatus, viral reactivation, and transplant outcomes, as well as current and evolving strategies for prevention and treatment of CMV-related complications that may have significant impact for alloHCT recipients. [ABSTRACT FROM AUTHOR]