Interferon gamma receptor deficiency is a rare autosomal recessive inherited disorder, with poor prognosis due to early-onset, recurrent, and disseminated mycobacterial infections. Hematopoietic stem cell transplantation (HSCT), the only curative treatment, is particularly difficult in these patients owing to a high rate of graft rejection. We report the first successful hematopoietic stem cell transplantation with an unrelated donor, performed in a schoolgirl with severe interferon gamma receptor 1deficiency caused by a novel mutation.