A 33-year-old Chinese male patient with severe aplastic anemia received matched sibling allogeneic hematopoietic stem cell transplantation using antithymocyte globulin containing conditioning regimen after 4 months of unsuccessful treatment with cyclosporine A. Following transplantation, the patient was immunosuppressed demonstrated by intermittent infections, including a varicella 3 months after transplantation. Although DNA-STR results on day +30 confirmed complete donor engraftment, repeat DNA-STR analysis performed more than 3 months after transplantation showed a mosaic phenotype. Cyclosporine tapering commenced early, but the last DNA-STR result confirmed complete graft rejection. On day +198, the patient presented with fever, skin boil in the right temporal region, severe pancytopenia, intrabodominal lymphadenopathy and hepatosplenomegaly. Within 1 month, superficial lymphadenopathy and right exophthalmos developed. Excisional lymph node biopsy pathology confirmed Kaposi's sarcoma (KS). The patient succumbed due to intracranial bleeding as a result of thrombocytopenia. This is the first study of KS that developed following stem cell transplantation for severe aplastic anemia. The precipitating factors underlying KS development in this case and its differentiation from post-transplant lymphoproliferative disorders are analyzed.