Objective: Electroconvulsive therapy (ECT) has been used in the treatment of several psychiatric disorders for decades, and the procedure's methodology developed significantly throughout the years. Current ECT procedure is a highly effective treatment, useful when pharmacotherapy fails, and able to produce quick results in life threatening situations. The mechanism by which ECT exerts its therapeutic effects is still unclear, and this is an area of active investigation today. Method: In this article, we perform a review of the available literature about ECT's mechanisms of action, focusing on specific actions that produce a therapeutic effect not only in depression, but also in psychotic states such as schizophrenia, in catatonia, and other pathologies, and also giving attention to predictors of treatment outcome, mechanisms of acute and chronic effects, aspects correlated with clinical relapse, mechanisms of superiority vs pharmacological treatment, and mechanisms underlying ECT's side effects. Results: ECT produces a large number of neurobiological effects, which interact among them and produce clinical improvement. We were able to identify some variables that allow the optimization and personalization of ECT procedures, some predictors of efficacy, specific mechanisms of action per pathology, mechanisms of superiority vs pharmacological treatment, mechanisms related with acute and chronic effects and related with clinical relapse. Conclusions: Further studies in this area may lead to better understanding of psychiatric disease pathophysiology, and may help in the development of new and improved pharmacological treatments. Identification of the mechanisms that are responsible for dramatic responses following a single ECT session and of more mechanisms related to clinical relapse is pressing in optimization of ECT treatment.