The present study was designed to assess the synergistic antitumor effects of anthracenylmethyl homospermidine (ANTMHspd), a novel polyamine conjugate, with alpha-difluoromethylornithine (DFMO) and to elucidate the mechanism of these effects on human leukemia HL60 cells. Cell proliferation was assessed by the MTT assay. Cell cycle, apoptosis and mitochondria membrane potential (MMP) were evaluated by flow cytometry. Caspases and cytochrome c were detected by Western Blot analysis. The combination treatment strongly inhibited cell proliferation, induced cell apoptosis and caused an accumulation in the G1 phase with an accompaniment decrease in S phase. Moreover, reduction of MMP, release of cytochrome c and activation of caspase-3 and caspase-9 but not caspase-8 were observed during the combination-mediated apoptosis. All these findings demonstrated that the combination treatment with DFMO and ANTMHspd resulted in synergistic antitumor effects on HL60 cells.