There is a lack of studies regarding the efficacy of electroconvulsive therapy (ECT) in children and adolescents. In this study, we aimed to assess benefits and harms of ECT in children and adolescents with major psychiatric diseases. We conducted a systematic search in PubMed, EMBASE, and PsycINFO for peer-reviewed articles written in English regarding the use of ECT as treatment for major psychiatric diseases in children and adolescents. This study consists of 192 articles, mostly case studies (n = 50), reviews and overview articles (n = 52), and retrospective studies (n = 30). We present an overview of evidence for ECT in children and adolescents with mood disorders, catatonia, schizophrenia, intellectual disability, self-injurious behavior, and other indications. This article is also a summary of international guidelines regarding the use of ECT in children and adolescents. We evaluated the overall quality of evidence by using Grading of Recommendations, Assessment, Development and Evaluations and found the overall level of evidence to be of low quality. There are no absolute contra indications for ECT in children and adolescents. Fears regarding cognitive dysfunction have not been reproduced in studies. Electroconvulsive therapy should be considered in severe, treatment-resistant mood disorders, catatonia, and schizophrenia, especially in older adolescents. High-quality studies are warranted to assess the efficacy of ECT, especially in these potentially life-threatening diseases.