This case report describes a domestic shorthair cat presumptively diagnosed with and treated for Acute Hemonhagic Dianhea Syndrome (AHDS). An eight year-old spayed female cat initially presented for acute onset open-mouthed breathing and vomiting. The cat was admitted into the intensive care unit, placed on intravenous fluids and supplemental oxygen; her open-mouthed breathing soon resolved. However, she developed hematemesis, bilateral epistaxis, profuse, watery diarrhea containing large quantities of frank blood, and signs of hypovolemic and septic shock. Diagnostics led to a presumptive diagnosis of AHDS, until recently known as Hem01Thagic Gastroenteritis (HGE). Treatment consisted of intravenous fluids, antiemetics, prokinetics, antacids, antibiotics, and a physiologic dose of steroids. The patient made a full recovery. AHDS is a well-known syndrome in dogs, but is not well characterized in cats. This report will compare this cat's clinical findings and disease progression with a typical case of AHDS in dogs, highlighting recent advances in our understanding of its etiology and treatment.