Imaging-guided photodynamic therapy (PDT) has been regarded as a promising strategy for precise cancer treatment. Because of their excellent modifiability and drug loading capacity, nanoparticles have played an important role in PDT. However, when traditional photosensitizers are made into nanoparticles, both their fluorescence and reactive oxygen species (ROS) generation efficiency are decreased due to a phenomenon known as aggregationcaused quenching. Fortunately, in recent years, several kinds of organic dyes have been developed with “abnormal” properties termed aggregation-induced emission (AIE). With enhanced fluorescence emission in the nano-aggregation state, the traditional obstacles mentioned above could be overcome by AIE luminogens (AIEgens). Herein, we provide a better combination of photosensitizers and nanoparticles, a kind of dual-functional AIE nanoparticle capable of producing ROS, to achieve targeted and imaging-guided in vivo PDT. Good contrast in in vivo imaging and obvious therapeutic efficiency were realized with a low dose of AIE nanoparticles as well as a low power density of light, resulting in negligible side effects. Our work demonstrates that AIE nanoparticles could play a promising role for imagingguided clinical photodynamic cancer therapy in the near future.