HLA-haploidentical hematopoietic stem cell transplantation from related donors has gained attention as an alternative treatment for patients who do not have HLA-identical siblings and lack the time to search for HLA-matched unrelated donors due to availability for nearly all individuals. As a key factor in the success of this approach is depletion of donor T cells, HLA-haploidentical transplantation has rapidly gained acceptance worldwide with the development of three platforms: 1) CD34-positive cell selection using CliniMACS®; 2) the conditioning regimen with anti-thymocyte globulin; and 3) a recently-developed, post-transplant cyclophosphamide regimen. Since the high efficacy of T-cell-depletion provides both sufficient suppression of GVHD and a high risk of opportunistic infection, there is an urgent need to strengthen the prevention of viral infections. On the other hand, conditioning with ATG and the post-transplant cyclophosphamide regimen are becoming the strategies mainly used in haploidentical transplantation because of high practicability and low risk of infection, though these platforms necessitate other drugs for GVHD prophylaxis due to the low efficacy of T cell depletion. Together with progress in these platforms, outcomes of haploidentical transplantation are comparable to outcomes of HLA-matched transplants. Currently, HLA-haploidentical transplantation is increasingly being recognized as a novel breakthrough in hematopoietic stem cell transplantation.