Pharmacists are increasingly recognized as an essential member of the multidisciplinary team for hematopoietic cell transplant (HCT) patients. However, until recently, their educational background, required training, and potential roles have not been well described. Therefore, the purpose of this manuscript is to provide supporting evidence for the HCT Clinical Pharmacist Role Description, which has been endorsed by several organizations including the American Society for Blood and Marrow Transplantation. This document provides justification for the various roles pharmacists fulfill with respect to medication management, transitions of care, patient and provider education, policy development, quality improvement, and research. Furthermore, evidence supporting the value, financially and otherwise, HCT pharmacists provide is reviewed. Pharmacists in the HCT setting are encouraged to report on novel practice models and potential impact of their services to increase awareness and utilization of HCT pharmacists.