Severe combined immunodeficiency (SCID) is one of the most serious inborn errors of immunity leading to a fatal infection in early infancy. Allogeneic hematopoietic cell transplantation (HCT) or elective gene therapy prior to infection or live-attenuated vaccination is the current standard of curative treatment. Even in the era of newborn screening for SCID, pretransplant control of severe infection is challenging for SCID. Multiple pathogens are often isolated from immunocompromised patients, and limited information is available regarding antiviral strategies to facilitate curative HCT. We herein present a case of successfully controlled pretransplant pneumonia after ribavirin and interferon-alpha therapy in an infant with RAG1-deficiency. A four-month-old infant presented with severe interstitial pneumonia due to a co-infection of rhinovirus and Pneumocystis jirovecii. The tentative diagnosis of SCID prompted to start antibiotics and trimethoprim-sulfamethoxazole on ventilatory support. Because of the progressive respiratory failure four days after treatment, ribavirin and then pegylated interferon-alpha were started. He showed a drastic response to the treatment that led to a curative HCT 32 days after admission. This patient received the genetic diagnosis of RAG1-deficiency. Currently, he is an active 3-year-old boy with normal growth and development. The review of literature indicated that rhinovirus had a comparable or rather greater impact on the mortality of pediatric patients than respiratory syncytial virus. Considered the turn-around time to the genetic diagnosis of SCID, prompt ribavirin plus interferon-alpha therapy may help to control severe rhinovirus pneumonia and led to the early curative HCT for the affected infants.