B-cell chronic lymphocytic leukemia (B-CLL) is an abnormal neoplasic proliferation of B cells, which accumulate mainly in the bone marrow and blood preventing both B cells development in the lymph nodes and the ability to fight against infection. The antitumor agents used in chemotherapy are aimed at inducing malignant cell death, thus limiting the growth and spreading of these cells. However, the lack of specificity for tumor cells exhibited by these agents causes undesirable side effects that have led to the investigation of new therapeutic strategies designed to specifically target malignant cells and thus trigger selective cell destruction. Dequalinium (DQA) is an antitumoral agent that selectively accumulates in the mitochondria and has been shown to display anticancer activity in cells from different malignancies. In the present study, the DQA-induced cytotoxicity in B-CLL cells was analyzed by measuring cell viability and cell death, either by necrosis or apoptosis. Our results support the importance of DQA as a selective and potential antileukemic drug with a higher cytotoxic effect on peripheral blood mononuclear cells from B-CLL patients than in those from healthy donors and encourage the performance of further studies in combination with other agents.