Nanomaterials have recently attracted much attention as efficient transducers for cancer photothermal therapy, based on their intrinsic absorption properties in the near‐infrared region. This study explores a novel therapy model with mitochondria‐targeting single‐walled carbon nanotubes (SWNTs), which act efficiently to convert 980‐nm laser energy into heat and selectively destroy the target mitochondria, thereby inducing mitochondrial depolarization, cytochrome c release, and caspase 3 activation. The laser+SWNTs process affords remarkable efficacy in suppressing tumor growth in a breast cancer model, and results in complete tumor regression in some cases. Laser+SWNTs could prove to be a promising selective local treatment modality, while minimizing adverse side effects.