Common variable immunodeficiency (CVID) is a relatively common form of immunodeficiency disorders which constitutes a mixed group of heterogeneous conditions linked by lack of immune globulin production and primary antibody failure. Recently, it is understood that various monogenic defects determine the variability in phenotype and have roles in the immunopathogenesis of CVID. In this review, the molecular defects related to CVID which are ICOS (inducible co-stimulator), TACI (transmembrane activator and calcium-modulator and cyclophilin ligand interactor), CD19, MSH5 (MutS Homologue 5 Mutations), BAFF-R (B cell activating factor receptor), CD20, CD81, CD21, LRBA (lipopolysaccharide-responsive beige-like anchor), and their genetic basis were aimed to be reviewed.