Dementia-related behavioral disturbances are mostly treated with antipsychotics; however, the observed beneficial effects are modest and the risk of serious adverse effects high. We report the case of a 57-year-old woman with severe early-onset Alzheimer's disease and severe agitation, whom we treated with electroconvulsive therapy (ECT). A significant clinical improvement was achieved over eight ECT sessions, which were tolerated well without cognitive worsening, and lasted approximately 3 months. Our case demonstrates the safe and effective use of ECT in pharmacotherapy-resistant severe agitation in Alzheimer's disease. The risk-benefit profile of ECT for dementia-related agitation should be further investigated in clinical trials.