Wiskott–Aldrich syndrome (WAS) is a rare X-linked primary immunodeficiency disorder characterized by the triad of eczema, thrombocytopenia, and severe and often recurrent infections. Despite the rarity of this disorder, our understanding of the molecular and cellular pathogenesis of WAS has continued to increase. Advances in the use of diagnostic tools, the provision of supportive care, and improvements in allogeneic hematopoietic stem cell transplantation have significantly reduced the morbidity and mortality associated with this disorder. Exciting advancements in the care of patients with WAS have also occurred, including the successful application of autologous gene-modified hematopoietic stem cell transplantation.