Acute abdominal pain is a common complaint in pediatric emergency departments. A complete evaluation is the key factor approaching the disease and should include the patient’s age, any trauma history, the onset and chronicity of the pain, the related symptoms and a detailed physical examination. The aim of this review article is to provide some information for physicians in pediatric emergency departments, with the age factors and several causes of non-traumatic acute abdominal pain. The leading causes of acute abdominal pain are divided into four age groups: infants younger than 2 years old, children 2 to 5, children 5 to 12, and children older than 12 years old. We review the information about acute appendicitis, intussusception, HenochSchnlein purpura, infection, Meckel’s diverticulum and mesenteric adenitis. In conclusion, the etiologies of acute abdomen in children admitted to the emergency department vary depending on age. A complete history and detailed physical examination, as well as abdominal imaging examinations, could provide useful information for physicians in the emergency department to narrow the differential diagnosis of abdominal emergencies and give a timely treatment. Acute abdominal pain is a common complaint in pediatric emergency departments. A complete evaluation is the key factor approaching the disease and should include the patient’s age, any trauma history, the onset and chronicity of the pain, the related symptoms and a detailed physical examination. The aim of this review article is to provide some information for physicians in pediatric emergency departments, with the age factors and several causes of non-traumatic acute abdominal pain. The leading causes of acute abdominal pain are divided into four age groups: infants younger than 2 years old, children 2 to 5, children 5 to 12, and children older than 12 years old. We review the information about acute appendicitis, intussusception, Henoch Schnlein purpura, infection, Meckel’s diverticulum and mesenteric adenitis. In conclusion, the etiologies of acute abdomen in children admitted to the emergency department vary depending on age. A complete history and detailed physical examination, as well as abdominal imaging examinations, could provide useful information for physicians in the emergency department to narrow the differential diagnosis of abdominal emergencies and give a timely treatment.