Background: Fibromatosis collis or pseudo-tumor of sternocleidomastoid in infancy is a rare cause of neck swelling in neonates. It is a congenital benign fibrous tumor developed from the sternocleidomastoid muscle, which if complicated, may lead to congenital torticollis. Case Report: Ultrasound of three week old neonate with right neck swelling showed fusiform thickening of the sternocleidomastoid muscle which showed heterogeneous echotexture.  The maintained fibrillar structure, no vascular or bony evasion suggested fibromatosis collis. Conclusion: If diagnosed correctly, it can be managed conservatively with physiotherapy, and unnecessary investigations can be avoided.