Background: Fibromatosis or desmoid tumors are rare (constitutes less than 3% of soft tissue tumor) benign tumors of musculo-aponeurotic origin with extensive tendency of local invasion causing morbidity. Case Presentation: We report a rare case of 30 year old male presented with left sided neck mass situated in left supra clavicular region. Ultrasonography and Magnetic resonance imaging (MRI) of neck revealed well defined soft tissue swelling of sized 7cm x 8cmx 8cm, present in left supra clavicular region. patient underwent surgical excision of mass. Histological and immunohistochemistry analysis confirmed the diagnosis of fibromatosis (desmoid tumor) of neck. Conclusion: Fibromatosis has unique aggressive behavior. Due to lack of set protocols for its management, treatment should be individualized and multi-modality treatment including radiotherapy and chemotherapy should be considered. We expect further awareness and study of this aggressive tumor by presenting our case.