A case of acute cholecystitis following giant puffball mushroom ingestion is described. A 64-year-old male ingested what was presumed to be a puffball mushroom, developed epigastric pain several hours later, and went to the emergency department. Patient blood work yielded elevated liver enzymes and bilirubin levels, with no change in coagulation studies. A mycologist associated with our regional poison center confirmed the mushroom to be a giant puffball mushroom which is recognized as a non-poisonous mushroom. After identification of the mushroom and recognition that it was unlikely the cause of the elevated liver enzymes, the workup was expanded, and the patient was found to have acute cholecystitis on imaging. This case highlights the added value of incorporating mycologists when the mushroom in question is available.TopicsToxicology, mycology, poison control/center, puffball mushroom, Calvatia, Lycoperdon.