The most common immunodeficiency in DiGeorge sequence patients is defects in T-cell production due to insufficient thymic tissue. However, because T-lymphocytes are important in regulating antibody responses, DiGeorge sequence is no longer regarded as a pure deficiency of cellular immunity but also a form of variable-combined immunodeficiency. Here we presented a 4-month-old male infant with characteristic facial dysmorphism, thymus dysplasia, tetralogy of Fallot, and documented deletion of chromosome 22q11.2 who had decrease B-lymphocyte numbers and hypogammaglobulinemia. The mitogen responses of T-lymphocytes function were normal with adequate number of CD4+ lymphocytes. This case report highlights the importance of evaluating not only the cellular but also the humoral immune function in patients with DiGeorge sequence.