Electroconvulsive therapy (ECT) is an extremely effective treatment modality for severe depression but is often associated with transient or persistent cognitive impairment. ECT-induced cognitive impairment, however, can serve as a deterrent to completion of treatment. We present a case of a prolonged post-ECT delirium lasting approximately 3 weeks in which donepezil, an acetylcholinesterase inhibitor, was used and was successful in shortening the duration of post-ECT delirium.