Acute acalculous cholecystitis is uncommon, although children are more likely to have this condition than adults. A 1,100-g premature baby girl with a gangrenous acalculous cholecystitis is reported. She presented with clinical and radiographic findings that were initially interpreted as necrotizing enterocolitis. An exploratory laparotomy demonstrated the presence of an acute gangrenous acalculous cholecystitis, and a cholecystectomy was performed. To our knowledge, this one of the smallest patients reported with this entity, and the first whose condition was initially diagnosed as necrotizing enterocolitis. It is important to recognize this entity and consider it in the differential diagnosis of premature infants, because in patients with necrotizing enterocolitis nonoperative management should be attempted initially, and patients with acute gangrenous cholecystitis most likely will require a laparotomy and cholecystectomy.