Epilepsy is a common neurological condition, with an estimated incidence of 50 per 100,000 persons. People with epilepsy may present with various types of immunological abnormalities, such as low serum immunoglobulin A (IgA) levels, lack of the immunoglobulin G (IgG) subclass and identification of certain types of antibodies. Intravenous immunoglobulin (IVIg) treatment may represent a valuable approach and its efficacy has important implications for epilepsy management. This is an updated version of the original Cochrane review published in Issue 1, 2011.To examine the effects of IVIg on the frequency and duration of seizures, quality of life and adverse effects when used as monotherapy or as add-on treatment for people with epilepsy.For the latest update, we searched the Cochrane Epilepsy Group Specialized Register (2 February 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (2 February 2017), MEDLINE (Ovid, 1946 to 2 February 2017), Web of Science (1898 to 2 February 2017), ISRCTN registry (2 February 2017), WHO International Clinical Trials Registry Platform (ICTRP, 2 February 2017), the US National Institutes of Health ClinicalTrials.gov (2 February 2017), and reference lists of articles.Randomized or quasi-randomized controlled trials of IVIg as monotherapy or add-on treatment in people with epilepsy.Two review authors independently assessed the trials for inclusion and extracted data. We contacted study authors for additional information. Outcomes included percentage of people rendered seizure-free, 50% or greater reduction in seizure frequency, adverse effects, treatment withdrawal and quality of life.We included one study (61 participants). The included study was a randomized, double-blind, placebo-controlled, multi-centre trial which compared the treatment efficacy of IVIg as an add-on with a placebo add-on in patients with refractory epilepsy. There was no significant difference between IVIg and placebo in 50% or greater reduction in seizure frequency. The study reported a statistically significant effect for global assessment in favour of IVIg. No adverse effects were demonstrated. We found no randomized controlled trials that investigated the effects of IVIg monotherapy for epilepsy. Overall, the included study was rated as low/unclear risk of bias. Using GRADE methodology, the quality of the evidence was rated as low.We cannot draw any reliable conclusions regarding the efficacy of IVIg as a treatment for epilepsy. Further randomized controlled trials are needed.