Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is potentially a curative therapeutic option for hematological malignancies. In clinical practice, transplantation associated complications greatly affected the final therapeutical outcomes. Currently, primary disease relapse, graft-versus-host disease (GVHD) and infections remain the three leading causes of a high morbidity and mortality in allo-HSCT patients. Various strategies have been investigated in the past several decades including human gamma delta T cell-based therapeutical regimens. In different microenvironments, human gamma delta T cells assume features reminiscent of classical Th1, Th2, Th17, NKT and regulatory T cells, showing diverse biological functions. The cytotoxic gamma delta T cells could be utilized to target relapsed malignancies, and recently regulatory gamma delta T cells are defined as a novel implement for GVHD management. In addition, human gamma delta T cells facilitate control of post-transplantation infections and participate.in tissue regeneration and wound healing processes. These features potentiate gamma delta T cells a versatile therapeutical agent to target transplantation associated complications. This review focuses on insights of applicable potentials of human gamma delta T cells reconciling complications associated with allo-HSCT. We believe an improved understanding of pertinent gamma delta T cell functions would be further exploited in the design of innovative immunotherapeutic approaches in allo-HSCT, to reduce mortality and morbidity, as well as improve quality of life for patients after transplantation. (C) 2015 Elsevier Ltd. All rights reserved.