Accessory spleen torsion is very rare condition especially in children. The aim of this study is to report the conservative treatment option. In April 2009 we observed a 10-year-old child affected by hereditary spherocytosis who reported acute abdominal pain without fever or vomiting. At hospitalization all blood tests were within normal value. Abdominal ultrasounds showed an increase in spleen volume and a solid round-shaped hypoechogenic formation with hyperechogenic areas in the lower pole without vascolarisation on color-Doppler scan. These findings suggested torsion of the accessory spleen. We opted for a conservative approach: analgesics on demand and antibiotics. After a week symptoms resolved spontaneously and patient was discharged in good health conditions. Follow-up ultrasound scans were performed at one week, three-six months and one year after hospitalization and showed a progressive reduction of the dimensions of the solid round-shaped formation. Accessory spleen torsion needs to be added to the differential diagnosis of cases of acute abdomen in children. Ultrasounds with eco-color-Doppler scans seem to be the best option for the diagnosis of such condition in the pediatric age since other diagnostic methods are more invasive and require sedation of patients. Once accessory spleen torsion is correctly diagnosed it is possible to opt for its conservative treatment.