Synovial sarcoma is uncommonly documented in the pelvis. Rarely, such cases have dealt with molecular analysis. A 19-year-old boy presented with pain and swelling in his left lower limb of two months duration. He developed acute urinary retention four days prior to his hospital admission, wherein radiological examination unraveled a large soft tissue mass, displacing his pelvic muscles, along with a lytic lesion involving his right pubic bone. Biopsy showed a cellular spindle cell sarcoma, exhibiting hemangiopericytoma-like vascular pattern with focal necrosis. Immunohistochemistry (IHC) showed positivity for vimentin, BCL-2, calponin and MIC 2. Cytokeratin (CK) and epithelial membrane antigen (EMA) were negative. MIB 1 count was 70% (high). P53 was positive. Diagnosis of a poorly differentiated synovial sarcoma was offered and confirmed with a positive t(X; 18) SYT-SSX2 translocation. This case highlights the value of molecular analysis in diagnosis of a synovial sarcoma at rare sites, especially when IHC results are equivocal and the biopsy material is limited.