About two thirds of patients with multiple myeloma and M-component in serum also have light chains in urine. However, the simultaneous presence of 2 Bence Jones proteins of different immunologic types in the same patient is rare. We describe the case of a 58-year-old woman with multiple myeloma, having 2 monoclonal light chains of both types (kappa and lambda) and an immunoglobulin G-lambda monoclonal protein in urine. The quantitative determination of light chains in urine was carried out using nephelometry, and Bence Jones proteinuria was confirmed by agarose gel immunofixation. To the best of our knowledge, this is the first reported case of double Bence Jones proteinuria after hematopoietic cell transplantation.