Viral infections are common causes of morbidity and mortality in patients undergoing hematopoietic stem cell transplantation (HSCT). In particular, allogeneic HSCT induces a profound immunocompromised state that may last up to 24 months post transplant, or longer in case of chronic graft vs host disease (GVHD). The common viruses affecting HSCT patients are HSV, VZV, CMV, EBV, adenovirus, HHV6, BK virus and upper respiratory viruses such as influenza, parainfluenza, and RSV. These infections typically occur in three distinct phases: pre‐engraftment, early postengraftment, and late postengraftment. This review will have two major sections, the first will discuss the epidemiology and natural history of different viral infections and second part will discuss preventive and therapeutic strategies among HSCT patients.