Antitumor photosensitizer-5 (Ru2) is a photosensitizer which effectively target tumor mitochondria with an IC 50 of 0.3 μM for phototoxicity to A549 cells. Under 460 nm light irradiation, antitumor photosensitizer-5 induces the generation of reactive oxygen species and NADH depletion, causes mitochondrial damage and activation of caspase-3 , inducing apoptosis and suppressing cell migration. Antitumor photosensitizer-5 has the potential to prevent the growth of malignant tumors, therefore, shows the potential to be applied to photodynamic therapy.