A 28-year-old man with a history of drug and alcohol abuse presented multiple times to the hospital over 2 months with an elusive constellation of symptoms, resolving spontaneously in each instance. This patient required a high level of care for management and stabilization, including 3 emergency department visits, 2 medical floor admissions, and 1 intensive care unit admission. In both the emergency department and inpatient setting, all laboratory and imaging study results, including gas chromatography/mass spectrophotometry of the urine, were negative/normal. A definitive diagnosis eluded multiple emergency medicine, critical care, and consulting physicians. His symptoms included altered mental status, vomiting, diaphoresis, and mydriasis. The patient later admitted using mushrooms to a nurse. In the absence of confirmatory testing, but supported by exclusionary and anecdotal data, we believe that our patient's symptoms are consistent with Psilocybe mushroom toxicity. We feel that had this been considered initially, the correct diagnosis would have led to a better utilization of resources, and we want to remind emergency physicians of the possibility of mushroom abuse in any similar clinical setting.