Delirium and agitation are commonly encountered after administration of electroconvulsive therapy (ECT). Management is generally fairly straightforward, although some patients may have a severe, prolonged, or refractory course. We recently cared for a 65-year-old man who consistently developed severe and very prolonged post-ECT delirium that did not respond to typical pharmacological agents; the duration of delirium was dramatically shortened by the addition of donepezil. Cholinesterase inhibitors may have a place in mitigating severe and prolonged post-ECT delirium.