Fibromatosis colli is a benign fibrous tissue proliferation of sternocleidomastoid muscle, which is usually observed during the first month of life, often associated with congenital torticollis. It should be differentiated from other neck masses in infants because the usual initial treatment of fibromatosis celli is conservative management and invasive therapy should be avoided. Fine needle aspiration cytology provides an excellent minimally invasive diagnostic way for evaluation of infantile neck masses. We describe three cases of fibromatosis colli diagnosed by fine needle aspiration cytology. All of them were younger than one month and presented as a neck mass. Clinical impressions were malignant tumors in two cases and fibromatosis colli in one case. Fine needle aspiration cytology revealed benign and mature fibroblasts and atrophic striated muscle fibers. The cytologic diagnosis was fibromatosis colli or benign fibous lesion.