Background: Desmoid tumors (aggressive fibromatoses) are rare soft tissue tumors seen in abdominal and chest regions. We report a patient with a rare significantly larger desmoid tumor of the chest wall with bone encasement and diaphragmatic involvement. Case Report: We are reporting a 25-year-old lady who presented with complaints of pain and swelling over right lower chest since last 2 years. MRI and Trucut biopsy revealed it to be a spindle cell neoplasm. Histopathological and immunohistochemistry following wide surgical excision revealed it to be a desmoid tumor. Conclusion: This case is discussed because of the rarity of desmoid tumors of the chest wall, complexity of rib and diaphragmatic involvement and surgical challenges.