Severe combined immunodeficiency is an inherited disease with profoundly defective T cells, B cells, and natural killer cells. X-linked severe combined immunodeficiency is the most common form. In this report, we describe a 4-month-old male infant who was admitted to our hospital with progressive breathlessness and abdominal mass. He was diagnosed with hepatoblastoma and presented a pneumocystis jirovecii pneumonia at the beginning of chemotherapy. Definitive diagnosis of X-linked severe combined immunodeficiency was established by DNA analysis of the interleukin 2 receptor gamma chain gene. This case is the first report which describes an X-linked severe combined immunodeficiency patient with hepatoblastoma.