In this study, we retrospectively examined 34 donor/recipient transplant pairs fully tested for the alleles HLA-A, B, C, DRB1, DQB1 and DPB1 in two different centers in Istanbul, Turkey. HLA-DPB1 disparity in at least one antigen level was 79.6% and only 20.6% of transplant pairs were fully identical for HLA-DPB1, in our study group. Neutrophil and thrombocyte engraftment successfully occurred in the entire study group. When the occurrence of severe (Grade III-IV) aGVHD was taken into account, we have observed that, non-permissive HLA-DPB1 mismatches were a significant factor for development of severe aGVHD (p= 0.019). There was a trend of increasing significance for the gut (p= 0.006) and liver (p: 0.054) aGVHD but not for skin aGVHD in non-permissive HLA-DPB1 mismatched transplantations. In multivariate analysis, non-permissive HLA-DPB1 mismatches remained as an independent factor for severe aGVHD. Our results did not show a significant impact of HLA-DPB1 mismatches on relapse. In survival analysis, both HLA-DPB1 disparities and non-permissive mismatches showed a decreasing trend of event free and overall survival times. Considering these results during donor selection may improve transplant outcomes in the setting of unrelated ASCT.