The rivastigmine patch is the only existing transdermal delivery system used for the treatment of Alzheimer's disease. Among the most common adverse events derived from its use are gastrointestinal events, particularly diarrhea. We report a clinical case of an 81-year-old patient admitted to our hospital under long-standing treatment with rivastigmine transdermal patch who presented with atypical watery diarrhea. Anamnesis showed that the patient presented with a likely infectious gastroenteric event, the diarrheal symptoms of which persisted upon resolution of the event and resolved only upon temporary discontinuation of acetylcholinesterase inhibitors. Failure to rapidly identify the causes of profuse diarrhea in older adults can have lethal consequences. When these symptoms occur, quickly recognizing the causes and providing proper management can be lifesaving.