A 62-year-old male was diagnosed with B-CLL and treated with Fludarabine-containing regimen which maintained the disease in partial response. Nine years after diagnosis, a rapidly growing systemic lymphadenopathy was observed, and a biopsy specimen revealed the presence of typical Hodgkin/Reed–Sternberg (HRS) cells, surrounded by T-lymphocytes and CLL cells. Sequencing analysis of the germline CDR3 region of the IGH gene showed that the HRS cells were clonally unrelated to the preexisting CLL cells and the HRS cells were composed of five different clones, leading to the molecular diagnosis of de novo lymphocyte-rich classic Hodgkin LPDs with SLL. Because the initial treatment was neither effective for classic Hodgkin LPDs nor for SLL, Bendamustine, Rituximab (BR) was started and complete remission was achieved, which has continued for more than one year so far. BR may be a good therapeutic option for both entities without causing hematological toxicity.