Bone marrow grafts offer a lower risk of graft-versus-host disease (GVHD) but require a surgical procedure and are associated with slower engraftment rates. Peripheral blood stem cells (PBSCs) enable faster engraftment and easier collection but have historically been associated with a higher risk of GVHD. Umbilical cord blood (UCB) grafts are readily available and carry no donor risk, with a higher tolerance for human leukocyte antigen mismatches and a lower risk of GVHD, but they are constrained by limited cell doses and slower engraftment. Recent advancements in transplant techniques—such as post-transplant cyclophosphamide to reduce GVHD rates in PBSC grafts, and cord blood expansion methods to increase the effectiveness of UCB grafts—have significantly improved transplant outcomes. Each graft source offers unique benefits and drawbacks that impact the selection process, factoring in patient age, disease type, donor availability, engraftment speed, immune recovery, GVHD risk, and logistical and financial considerations. These complexities highlight the need for a comprehensive and tailored approach to graft source selection, alongside adherence to guidelines and best practices, to optimize outcomes in allogeneic hematopoietic cell transplantation.