Perforation of a duodenal ulcer (DU) into the retroperitoneal space presenting with clinical features of acute appendicitis is known as Valentino's syndrome. Post duodenal perforation, the gastric and duodenal fluids tend to settle in the right paracolic gutter causing peritonitis and clinically mimicking acute appendicitis. Only three cases of Valentino's syndrome have been reported till date in the published literature and there is only one previous report of its preoperative imaging diagnosis. To our knowledge, this is the first reported case of preoperative imaging diagnosis in a surgically confirmed case of Valentino's syndrome. In most cases, patients with undiagnosed Valentino's syndrome are operated for acute appendicitis, and on finding a normal appendix, search is made for the cause of peritonitis, which then leads to retroperitoneal perforation of duodenum. The diagnosis of Valentino's syndrome by computed tomography (CT) imaging is easy and can help in avoiding the surgery or directing the surgeon directly to the repair of the duodenal perforation. It is, therefore, essential for emergency physicians, surgeons, and radiologists to know about this entity and consider it in the differential diagnosis.