In vitro photoacoustic therapy using modified single-walled carbon nanotubes (SWNTs) as “bomb” agents is a newly reported approach for cancer. Herein, a mitochondria-targeting photoacoustic modality using unmodified SWNTs and its in vitro and in vivo antitumor effect are reported. Unmodified SWNTs can be taken up into cancer cells due to a higher mitochondrial transmembrane potential in cancerous cells than normal cells. Under the irradiation of a 1064 nm pulse laser, 79.4% of cancer cells with intracellular SWNTs die within 20 s, while 82.3% of normal cells without SWNTs remain alive. This modality kills cancer cells mainly by triggering cell apoptosis that initiates from mitochondrial damage, through the depolarization of mitochondria and the subsequent release of cytochrome c after photoacoustic therapy. It is very effective in suppressing tumor growth by selectively destroying tumor tissue without causing epidermis injury. Taken together, these discoveries provide a new method using mitochondria-localized SWNTs as photoacoustic transducers for cancer treatment.