Teratoma of the neck is a rare extra-gonadal teratoma. Although it can be seen in adult, most of the cases present in fetal life or early childhood. Grading and classification of teratoma is important for management and prognosis. Decision making between mature and immature teratoma is sometime challenging if it is not composed of extensive unusual neuroectodermal tissue component. We reported a rare case of huge congenital mature cystic teratoma composted of various neuroectodermal tissues in an 8-month-old boy; it was located at the lateral neck and mimicked congenital cystic hygroma. A literature review was done to grade and classify the tumour.