Severe combined immunodeficiency disorders (SCID) are a genetically heterogeneous group of inherited defects characterized by severe abnormalities of immune system development and function that lead to a wide spectrum in clinical manifestations. A subgroup of patients presents a disabling and life-threatening clinical course. In these cases, allogeneic hematopoietic stem cell transplant provides a curative approach. The occurrence of SCID-associated lymphoproliferative disorders is rare and occur mostly in adenosine deaminase-deficient severe combined immunodeficiency disorders, after allogeneic hematopoietic stem cell transplant. Epstein Barr virus infection is present in the majority of individuals with primary immunodeficiency developing lymphoma, revealing compromised anti-tumour surveillance of virally transformed cells. Herein, we report a rare case of diffuse large B cell lymphoma occurring in an Epstein Barr virus negative, non-transplanted X-linked severe combined immunodeficiency 4-months-old infant, successfully treated with immunotherapy and allogeneic stem cell transplantation. This case suggests that Epstein Barr virus -independent mechanism of neoplastic transformation must take action in severe combined immunodeficiency associated lymphoma and unveils the curative potential of donor T cells after allogeneic transplantation.