We report a hepatic monophasic synovial sarcoma in a 60-year-old woman who presented with right upper quadrant pain subsequent to an intrahepatic bleed from a highly vascular tumor mass. Imaging studies showed a dominant tumor mass in the right hepatic lobe with multiple satellite nodules. A detailed physical examination and radiologic workup failed to reveal a primary tumor elsewhere. A right partial hepatectomy was performed with a preoperative differential diagnosis of angiosarcoma versus hepatocellular carcinoma. The morphologic, immunophenotypic, and cytogenetic findings (t(X;18)(p11.2;icq11.2)) were consistent with a monophasic synovial sarcoma. Postoperative clinical evaluation of the extremities and a positron emission tomographic scan performed 4 weeks after surgery showed no evidence of recurrent or metastatic disease. The patient was started on an aggressive 4-drug chemotherapy regimen, but died 3 months thereafter from widespread metastatic disease. No autopsy was performed. The presence of multiple lesions in the liver certainly suggests the possibility of metastatic disease. It would, however, be very unusual for a synovial sarcoma to present as an occult primary, and the negative radiologic workup 1 month after the partial hepatectomy also argues against this possibility. The clinical presentation, radiographic findings, and subsequent course in this patient was therefore most consistent with a primary monophasic synovial sarcoma of the liver.