Choosing Wisely encourages dialogue about reducing unnecessary procedures, tests, or treatments in healthcare. The American Society for Blood and Marrow Transplantation (ASBMT) and Canadian Blood and Marrow Transplant Group (CBMTG) established a Choosing Wisely BMT Task Force whose objective was to create a list of top 5 practices in blood and marrow transplantation to be questioned. The Task Force consisted of representatives from ASBMT's Quality Outcomes, Education, and Practice Guidelines committees; ASBMT's Pharmacy Special Interest Group; CBMTG Program Directors; and Center for International Blood and Marrow Transplant Research (CIBMTR). Suggestions for current transplantation practices to question were elicited from the CBMTG Program Directors; members of ASBMT's Quality Outcomes, Practice Guidelines, and Education committees; and chairs of the CIBMTR scientific working committees. We received 119 unique suggestions that were ranked based on their potential impact on harm reduction, cost reduction, necessity of the test or practice, and the strength of available evidence. Through a modified Delphi process, suggestions were narrowed down to 6, which were then subjected to systematic reviews. The final 5 recommendations focus on graft source for patients with aplastic anemia, corticosteroid dose for initial treatment of graft-versus-host-disease, optimal number of umbilical cord blood units for transplantation, graft source in matched unrelated donor transplantation, and use of prophylactic intravenous immunoglobulin in transplant recipients. These Choosing Wisely BMT recommendations are relevant to the current clinical practice of blood and marrow transplantation and focus on tests, treatments, or procedures that may be harmful, wasteful, or for which there is no apparent clinical benefit.