Refractory ascites as the only presenting feature of an extramedullary plasmacytoma complicating end-stage renal disease and HIV infection has not been described yet. We describe a case of a 39-year-old female with HIV-associated nephropathy manifesting with ascites formation after transition from peritoneal dialysis (PD) to hemodialysis (HD). Earlier on, she received cycler-assisted PD for 5 years uneventfully. A few weeks after HD transition, a striking refractory ascites developed requiring multiple paracenteses (5 - 7 L every second week). Serum protein electrophoresis showed hypoalbuminemia with only small amount of monoclonal IgG-κ at 0.30 g/dL. Serum immunofixation electrophoresis showed polyclonal immunoglobulins with polyclonal light chains. Both κ and λ light chains were increased, at 66.86 mg/dL (reference range: 0.33 - 1.94) and 18.55 mg/dL (reference range: 0.57 - 2.63), respectively, with a ratio of 3.6 (reference range: 0.26 - 1.65). However, an ascitic fluid analysis showed a marked increase in plasma cells with a κ : λ ratio greater than 5 : 1. Omental biopsy confirmed κ-restricted plasma cells. Multiple myeloma work-up with skeletal survey showed no evidence of focal osseous lesions, while bone marrow aspiration and biopsy also remained unremarkable. Accordingly, the diagnosis of omental extramedullary plasmacytoma with malignant ascites was confirmed. Conversion from PD to HD may unmask an underlying pathology favoring ascites formation.