Previous, Intravenous Immunoglobulin (IVIG) has been used for treatment of patients with immunodeficiency. However, recent studies have shown that IVIG is a suitable approach for treatment of inflammatory and autoimmune diseases. Although the exact mechanism of IVIG action is not well known, recent findings have demonstrated that IVIG impacts on expression and function of FC receptors of immunoglobulins, modulation of complement activation and cytokines. In addition, IVIG regulates cell proliferation, affects on differentiation of T, B and dendritic cells. Its side effects are classified into three categories, including immediate side effects (which can occur during infusion, including anaphylaxis reactions, facial flushing, and dyspnea), delay effects (which in a few hours a few days after the injection occur as side effects on the skin, lung, kidney, aseptic meningitis, arthritis, cerebral symptoms, leukopenia, and hemolysis) and late side effects (such as transmission of infectious agents). In this review, we are summarizing recent applications, mechanism and side effects of IVIG.