Intravenous Immunoglobulins (IVIg) are administered both as replacement therapy for certain immunodeficiencies and as immunomodulatory therapy for some autoimmune diseases. While the treatment with IVIg is approved in only a few autoimmune diseases, the number of off-label indications is increasing. The varied mechanisms by which IVIg attains its beneficial effect are diverse. There is much evidence for the beneficial and safety profile for IVIg in low as well as high-dose protocols. Patients prone to develop thrombotic events should be advised about the risk of IVIg therapy especially at high doses. This paper updates the mechanisms of action of IVIg as well as recent off-label indications.