Electroconvulsive therapy is a rapid and effective treatment of severe depression that has been shown to quickly decrease or eliminate suicidal thoughts and behaviors. We describe the case of an 88-year-old man hospitalized for a carefully premeditated suicide attempt with highly lethal means. He was treated with a single electroconvulsive therapy (ECT) and improved markedly. His suicidal ideation remitted, and the patient was still free of suicidal ideation at 5 months of follow-up. We discuss the effect of ECT on suicidal ideation, the benefit of minimizing the number of total ECT treatments, and the possible biological markers of change after a single treatment in an ECT-naive patient.