PTPN22 is a negative regulator of T-cell activation. The C1858T PTPN22 polymorphism has been associated with autoimmune diseases. The role of PTPN22 in immune response and autoimmune diseases suggested that PTPN22 polymorphism could impact outcome of allogeneic hematopoietic stem-cell transplantations that is impaired by immunological and infectious complications. One hundred ninety-two patients who received a non-T-depleted bone marrow transplant from a human leukocyte antigen-identical sibling donor were included in this study. Donor PTPN22 C1858Tpolymorphism was not associated with severe acute graft-versus-host disease, relapse, survival, cytomegalovirus, and fungal infections, but significant with severe bacterial infections (24% for donor CC vs. 0% for donor CT+ TT genotypes, P= 0.003). The association was confirmed by a multivariate analysis (P= 0.036, hazard ratio= 2.28, 95% confidence interval= 1.06–4.90). This could improve the genetic risk assessment of severe bacterial infections in allogeneic hematopoietic stem-cell transplantations.