The treatment of pediatric severe aplastic anemia (SAA) with allogeneic hematopoietic stem cell transplantation (allo-HSCT), presents major challenges including the risks of graft failure, septic complications, and graft-versus-host disease (GVHD). Additive infusions of human umbilical cord derived mesenchymal stem cell (hUC-MSC) may be administered to improve patient survival. We retrospectively examined 37 pediatric patients with SAA who received allo-HSCT and subsequent infusions of hUC-MSC suspension at a dose of 1.0 × 10 6 /kg. The times and doses of hUC-MSC infusions were increased in patients with severe GVHD. All patients received hUC-MSC infusions. The median time to post-transplantation neutrophil count of greater than 0.5 × 10 9 /L was 14 days (range, 11-20 days) and time to post-transplantation platelet count of greater than 20 × 10 9 /L was 19 days (14-29 days). The overall frequency of acute GVHD (aGVHD) was 45.9% (17/37). These aGVHD episodes occurred at a median time of post-transplantation 47 days (15-83 days). The frequency of chronic GVHD (cGVHD) was 18.9% (7/37); cGVHD developed from aGVHD in 10.8% (4/37) of patients. The GVHD-associated mortality rate was 18.9% (7/37) and aGVHD-specific mortality rate was 8.1% (3/37). The median overall survival time was 35 months (9-67 months) and the three-year overall survival rate was 74.2% (28/37). Seven patients died of GVHD, one patient died of a severe invasive fungal infection, and one patient died of renal failure. In conclusion, post-transplantation hUC-MSC infusions seemed to be safely infused in children with SAA who have previously received allo-HSCT. © 2014 Informa Healthcare USA, Inc.