Two copper complexes, [Cu(qbm)Cl₂]₂ (1) and [Cu(qbm)Br(PPh₃)] (2) (where qbm = 2-(2′-quinolyl)benzimidazole), have been prepared and characterized. The interactions of both complexes with calf thymus DNA (CT-DNA) were detected by absorbance and emission spectroscopy methods; the results showed that both complexes were bound to CT-DNA via an intercalative mode. In addition, the two complexes significantly exhibited the free radicals dependence of DNA cleavage activity. MTT assays revealed that complex 2 showed good cell proliferation inhibitory activity against four different human cancer cell lines (SMMC7721, BGC823, HCT116 and HT29), particularly with HCT116 cells. Furthermore, morphological changes and flow cytometry analyses indicated that complex 2 can induce HCT116 cell death by apoptosis. These findings should promote the development of metal-based complexes for use as novel chemotherapeutic agents.