A plasma-assisted strategy for densely doping indium to SnO(2) nanostructures for gas-sensing applications is reported. The morphology, structure, and composition of the as-prepared nanostructures were characterized by field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectrometry (XPS), respectively. The results show that the densities of hydroxyl and carboxyl groups of the coral-like SnO(2)/carbonaceous nanocomposites are remarkably improved by using a plasma treatment (PT), which enables them to adsorb a large quantity of indium ions and thereby enhance the doping. In gas-sensing measurements, it is found that the sensor is sensitive to chlorobenzene with a high response and short response and recovery times. Besides, the gas-sensing properties of the sensor based on the In-doped SnO(2) with PT are greatly improved compared with sensors based on In-doped SnO(2) without PT and pure SnO(2). The enhanced doping and the special coral-like structure are demonstrated as the mechanism of improvement. The kinetic processes of gas adsorption and desorption are also investigated. Furthermore, it is revealed that chlorobenzene can be clearly identified from some gas references by using principal component analysis, exhibiting a good selectivity. Our findings not only provide a promising building block for developing a sensitive and selective gas sensor for environmental monitoring, but also demonstrate a novel plasma-assisted strategy which could be potentially developed as a general method for dense doping of nanomaterials.