Aggressive fibromatosis (desmoid tumor) is one of the rare soft tissue tumors of childhood. It is commonly located in the head and neck region. Histopathologic nature of the tumor is benign and it lies between benign fibrous lesions and fibrosarcomas. Although it does not metastasize, it shows a local aggressive behaviour. The usual therapeutic approach is extensive surgical resection. Insufficient surgical resection may lead to recurrence and invasion of neighbouring tissues and thus may be fatal. A 4-year-old female patient referred to our clinic for a painless mass in the neck was operated twice and followed-up for five years. Tumor recurrence or functional problems were not observed during the follow-up period. In these cases, differential diagnosis should be made with fibrosarcoma, fibroma, giant cell lesions and fibrous dysplasia and it should be considered in young patients submitting with a mass in the head and neck region in early childhood.