Allogeneic hematopoietic stem cell transplantation (HSCT) is curative for chronic granulomatous disease (CGD), but many patients lack a suitably matched related donor. We report successful outcomes after mismatched, unrelated-donor umbilical cord blood transplantation (uUCBT) in two boys with X-linked CGD. Both patients experienced autologous recovery after first transplants, required second transplants to achieve durable donor engraftment, and are alive 27 and 15 months post-transplant. Both had invasive fungal disease and received granulocyte transfusions. In conclusion, uUCBT is effective in children with CGD, but immunosuppression in the conditioning regimen may need to be increased to decrease the risk of graft rejection.