Herein, we describe a case of a female patient in whom B cell chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) were diagnosed simultaneously. She presented with anemia, thrombocytopenia and splenomegaly. Flow cytometry demonstrated two immunophenotypically distinct CD5-positive monoclonal B cell populations. Peripheral blood fluorescence in situ hybridization (FISH) was positive for IGH/CCND1, consistent with t(11;14) translocation. She received 6 cycles of bendamustine 70 mg/m2/day for 2 days and rituximab on the first day every 4 weeks along with granulocyte-colony stimulating factor. She had an excellent response, and repeat computed tomography after her third cycle of chemotherapy revealed no organomegaly or lymphadenopathy. Her peripheral blood lymphocytosis also resolved. Bone marrow examination revealed no detectable flow-cytometric evidence of MCL or CLL. Repeat cytogenetic and FISH analysis were also normal. The patient remains in complete remission 20 months after her initial diagnosis and is receiving maintenance rituximab 375 mg/m2 weekly for 4 weeks every 6 months for 2 years.