There are currently over 5,000-known species of mushrooms worldwide. Only 20-25% of mushrooms have been named, and 3% of these are poisonous. More than 95% of mushroom poisoning cases occur due to difficulties associated with the identification of mushroom species. Most of the fatal mushroom poisoning cases recorded to date have been related to the Amanita species. Until now, a case of fatal poisoning caused by Macrolepiota neomastoidea (M. neomastoidea) has not been reported in Asia. A 57-year-old male patient was admitted to the emergency room with nausea, vomiting, diarrhea, and abdominal pain. He reported ingesting wild mushrooms with his mother and sister about 2 days ago. His mother and sister were treated with only supportive care, but he was admitted to the intensive care unit and underwent liver transplantation due to acute liver failure. We are reporting a case of fatal M. neomastoidea intoxication from wild mushrooms, a rare case of mushroom poisoning. (Korean J Gastroenterol 2018;71:94-97)