Acute appendicitis is the most common non-obstetric reason of abdominal pain in the pregnancy, causing significant increase of maternal and fetal morbidity and mortality. This is a case report of a patient in the third trimester of pregnancy in whom perforated appendicitis caused purulent peritonitis. She was operated as an emergency case and cesarean section was performed. After the surgery and antibiotic administration according to drug susceptibility test, her postoperative course was uneventful. Delayed diagnosis of the acute appendicitis leads to increased rate of appendicular perforation, with numerous maternal and fetal complications. In cases of suspected appendicitis during pregnancy, surgical exploration is indicated, either by laparoscopy or laparotomy. Laparotomy is the method of choice in cases after 20 weeks of pregnancy and whenever signs of diffuse peritonitis are present.