Objective: This article is a review of research regarding ketogenic diet in treatment of drug-resistant epilepsy in mentally retarded children. Method: A literature search was conducted using Magiran, PubMed and reference books nutrition. Results: There are valid scientific documents that show this diet reduces seizures in these children. The most common usage of this diet is for children with epilepsy which despite the use of anti-epileptic drugs, their seizures are continued.  Conclusion: Ketogenic diet has an important role in the treatment and control of seizures in refractory to treatment epilepsy and this  approach  should be considered by pediatric neurologists as a alternative treatment in mentally children who affected by drug-resistant epilepsy.