Ectopic thyroid tissue is ubiquitous in the body, most frequently seen at the base of tongue, accounting for approximately 95% of reported cases. Branchial cleft cyst, a congenital abnormality, can occasionally harbor thyroid tissue inside the cyst. These ectopic thyroid tissues can develop the same disease as the orthodox thyroid gland, including the malignant diseases. Papillary thyroid carcinoma arising in the branchial cleft cyst was extremely rare, total of only 14 cases were reported in the literature. Herein, I report additional case which was discovered incidentally after surgery.