Despite the availability of electroconvulsive therapy (ECT) and being one of the safest modalities of treatment, the use of ECT is still underused in patients with mental retardation with catatonia. However, the available limited literature suggests that ECT can be used safely with proper monitoring and assessment, especially in those presenting with catatonia in mental retardation. We treated a 17-year-old boy who presented to us with catatonia with mental retardation with a course of 12 ECT, with which the catatonia resolved completely. Review of the literature suggests that the occurrence of catatonia is rare in mental retardation. However, ECT can be used in a rare case with precautions.