The ultrasensitive and selective diagnosis along with efficient therapy in earliest stage of cancer has been enormously highlighted by a better means to treat the cancer. Herein, Gd (III) chelated polyaniline nanoparticles (GPNPs) was synthesized to be served as a highly T 1 enhanced contrast agents and Near-Infrared photothermal therapy probes. In addition, therapeutic antibody was conjugated on the surface of GPNPs for the targeted theragnosis. Fabricated GPNPs significantly reduced the T 1 of water protons with as well as represented photothermal ability. The physicochemical properties and biocompatibilities of GNPSs were fully characterized and GPNPs exhibited excellent tumor targeting ability. Consequently, GPNPs exhibited strong potential for efficient diagnosis of cancer in MR imaging and photothermal ablation of epithelial cancer cells.