Introduction: Desmoid tumor also known as aggressive fibromatosis, is a rare, locally invasive, non-metastasizing soft tissue tumor. They arise from any part of the body in different types of connective tissues. Infiltration of the bladder is usually rare and very few cases have been reported till date. Case report : 35/F presented with mass in the suprapubic region and lower abdominal pain since 1 month. Total abdominal hysterectomy + 8 years with pfananstiel incision. Per abdomen- soft, mass about 5 × 6 cm was palpable over the lower abdomen in the suprapubic region with tenderness. Fnac showed features suggestive endometriosis of bladder wall. Cect revealed? Ca bladder/ endometriosis of bladder. In view of high clinical suspicion (no h/o cyclical bleeding and cyclical pain). Cystoscopy was done which showed mucosal edema in right lateral wall with no mass in bladder with normal cystoscopy findings. Diagnostic laparoscopy and biopsy from the mass and right lateral bladder wall was performed. Histopathological diagnosis was features are those of collagen forming fibrous lesion suggestive of fibromatosis. Hence surgical excision was planned. Complete excision of the mass was done. Final histopathology report was features suggestive of fibromatosis with no evidence of endometriosis/epithelial malignancy. Following surgery patient improved and was asymptomatic. Discussion: Desmoid is a rare tumor, with reported incidence of 2–4 per million population and accounts for 0.03% Of all neoplasms. Desmoid tumor arises from myofibroblast, lacks a true capsule, usually infiltrates into adjacent muscle bundles. But the infiltration of the bladder is rare. The etiopathogenesis is multifocal. Mutation in apc or beta catenin genes is seen. Complete excision of the mass with sufficient margins of anterior rectus sheath with deroofing of the tumor with bladder wall was done. Final histopathology report was features suggestive of fibromatosis with no evidence of endometriosis/epithelial malignancy. Conclusion: The course of desmoid tumor is unpredictable, there can be spontaneous regression, long-lasting mass and/or progression of disease can occur.5 Currently preferred management for asymptomatic cases may be “wait and see” approach. Tumors showing increase in size and/ or causing symptoms require active management. Keywords: Desmoid; Bladder; Excision.