We describe a rare case of synchronous mantle cell lymphoma and metastatic prostate cancer to bone marrow as the second malignant disease. Various diagnostic procedures, including bone marrow aspiration ,bone marrow biopsy, flow cytochemistry and immunohistochemistry analyses together contributed to the detection of metastasis of prostate cancer and synchronous lymphoid cell proliferation in the bone marrow. The association between these two disorders is poorly understood however, some studies show that bone marrow microenvironment may play a crucial role. The need for further research in this regard is required to unfold this fascinating association