Background: Neonatal appendicitis is a rare condition and high mortality rate. Clinical presentations are usually atypical combine with nonspecific subclinical make preoperative diagnosis is difficult. We pres ent a 15-day-old infant with acute perforated appendicitis that was diagnosed and successfully operated at Hue Central Hospital. Case report: A male newborn 15-day-old was hospitalized at Neonatal Intensive Care Unit with irrita bility, bilious vomiting, and abdominal distension, and fever, with high white blood cell count and C-reactive protein level. The baby was initially diagnosed with neonatal sepsis from the gastrointestinal tract, 2 days after the baby condition was more severe, indicated operation with the diagnosis peritonitis may be due to necrotic enteritis. Postoperative diagnosis acute perforated appendicitis with peritonitis. Postoperative the patient was stable and discharged after 6 days later. Conclusion: No age is free from the risk of appendicitis. Preoperative diagnosis of acute appendicitis in neonates is difficult due to nonspecific clinical and subclinical presentation with the extreme rarity of the disease.