Five young patients with a long history of severe aplastic anemia (SAA) who had failed initial CSA treatment and lacked a HLA-matched sibling donor, underwent co-transplantation of unrelated donor peripheral blood stem cells (UD-PBSCs) and umbilical cord mesenchymal/stroma stem cells (UC-MSCs). After FLU + CTX + ATG ± 2GY TBI conditioning, all patients received UD-PBSCs and UC-MSCs. There were no side effects attributable to the infused MSCs, and no severe complications or infections were observed in any patient after transplantation. After transplantation, one patient experienced primary graft failure, the reason for which may be related to a long history (>17 years) of SAA. The other four patients achieved complete hematopoietic recovery and complete donor hematopoietic chimerism. We did not observe severe aGVHD or cGVHD. These data suggest that co-transplantation of UD-PBSCs and UC-MSCs is an acceptable alternative treatment for young patients with a long history of intensively treated SAA.