Allogeneic bone marrow transplantation (allo-BMT) is followed by a period of profound immune deficiency, which results in significant susceptibility to infections and limits the extensive application of this approach in clinic. Here, we transduced human interleukin-7 (IL-7) gene into donor-derived bone marrow stromal cells (MSCs) using adenovirus vector, and transplanted this gene-engineered MSCs (MSC-IL-7) into lethally irradiated C57BL/6 mice to investigate their effects on immune reconstitution following allo-BMT. Recipient mice receiving MSC-IL-7 cells plus T-cell-depleted bone marrow cells of BALB/c mice showed a significant increase in thymopoiesis and homeostatic expansion of peripheral T lymphocytes. Furthermore, injection of MSC-IL-7 cells following allo-BMT protected the host from the lethality caused by acute graft-versus-host disease (GVHD) and prevented the occurrence of GVHD induced by transplanted T cells. Thus, the use of MSC-IL-7 cells may be therapeutically useful for enhancing immune reconstitution without aggravating GVHD in allo-BMT mice.