Right colonic and cecal diverticulitis can mimic acute appendicitis. A 14-year-old, 105-kg boy presented at the emergency department with symptoms mimicking acute appendicitis. Surgery revealed a case of perforated solitary cecal diverticulitis. Diverticulosis is a disease known to be common in adulthood, but the incidence is increasing in childhood. Therefore, emergency room residents and pediatric surgeons need to keep this diagnosis in mind in the differential diagnosis of acute appendicitis. Early clarification of the etiology will enable the planning of the best treatment strategy.