A 7 year-old girl was admitted to our hospital with high grade fever and redness, swelling and tenderness in left neck. CT scan revealed cyst formation (4.5x3 cm) in left lobe of thyroid with swelling of surrounding lymphonodes. We diagnosed her as acute suppurative thyroiditis and treated her with intravenous antibiotics infusion and incisional drainage. After the treatment, the clinical course was uneventful. Pharyngograph revealed left piriform sinus fistula.