The loss of inflammatory regulation resulting from the absence ofB-lymphocytes leads to a risk for autoimmune and autoinflammatorycomplications. There is no data on the use of Vedolizumab in patients withX-linked agammaglobulinemia (XLA) as well as children with another primaryimmunodeficiency (PID) diseases. A 4-year-old boy was admitted to our clinicwith a history of recurrent respiratory tract infections. He was diagnosedwith XLA based on extremely low immunoglobulins, very low level of B cells,genetic mutation of BTK gene, and family history. At the age of 8, he sufferedfrom intermittent fever attacks, abdominal pain, weakness, oral aft, and weightloss. His clinical and laboratory features were consistent with inflammatorybowel disease. Histopathological examination of the biopsy material obtainedfrom terminal ileum, colon and cecum showed Crohn’s disease. Initially, hewas treated with prednisolone and infliximab. Because of the lack of response,infliximab treatment was switched to adalimumab. Terminal ileum wasresected to relieve obstruction complication. Although he had been treatedwith adalimumab, a significant improvement was not observed. Vedolizumab(Entyvio™), a humanized monoclonal antibody α4β7 integrin-receptorantagonist, was commenced. After treatment with vedolizumab, his feverand abdominal pain attacks reduced, his total daily calorie intake increasedand weight gain improved. He began to walk again and continued his schooleducation properly. No side effects were observed in 18 months. This is thefirst immunocompromised child treated with vedolizumab. The symptoms ofthe patient receded and no side effect were seen during the treatment.