One way to overcome some limitations of conventional cancer therapy is via the selective delivery of anticancer drugs to specific organelles within the target cancer cells. This strategy can maximize potency and minimize off-target side effects of the drugs. Amongst the cellular organelles, the mitochondrion hosts several putative drug targets of cancer therapy as the organelle plays key functions in different physiological and pathological cellular processes, such as programmed cell death. Hence, mitochondria are an appealing target for cancer therapies. Many heptamethine cyanine dyes have been demonstrated to preferentially localize in mitochondria and employed as imaging probes. The mitochondrial targeting ability is believed to be associated with the delocalized lipophilic cationic nature of the molecules. Indeed, we and others have demonstrated depolarization of mitochondrial membrane prevents accumulation of cyanine dyes in mitochondria. Moreover, we recently showed that tri-and pentamethine cyanine dyes can function as delivery vectors selectively targeting mitochondria with moderate preference toward tumor cells. It was therefore intriguing to us to investigate whether the addition of a cell-targeting component could further improve the cell selectivity of the conjugates.