This case study reported a 17-year-old female of common variable immunodeficiency (CVID) associated with bronchiectasis, pernicious anemia and mosaic trisomy 8. Clinically this patient presented with recurrent sinopulmonary infections, intractable diarrhea, macrocytic anemia, and primary amenorrhea. Immunological tests showed pan-hypogammaglobulinemia and a decrease of peripheral blood B cells (4%) and CD4+ cells (25%). Lymphoproliferative responses to mitogen (PHA) and specific antigen (BCG) were profoundly impaired in the patient in comparison to those in control. Production of interleukin 4 (IL-4) and gamma interferon (IFN-gamma) in the in vitro lymphoproliferation was also profoundly depressed. Pernicious anemia demonstrated by larger MCV (112.9 fl) and hyper-segmental granulocytes on peripheral blood smear responded to parental administration of vitamin B12. Interestingly, she had a mosaic trisomy 8 in peripheral blood mononuclear cells but normal 46XX karyotype in the bone marrow cells. To our knowledge, this is the first case of CVID associated with mosaic trisomy 8 reported in the literature. As the case exemplifies, CVID should be considered when the physicians evaluate the patient presenting with recurrent sinopulmonary infections, diarrhea, malnutrition, and pernicious anemia. It requires further study to explore whether the genes in the chromosome 8 are linked to CVID.