Ba-doped CeO2 nanowires were obtained from CeO2 particles through a facile composite-hydroxide-mediated (CHM) route. The products were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscope (HRTEM). The formation process of the product was discussed. Humidity sensors based on the source material CeO2 particles, Ba-doped CeO2 nanowires grown for 12 and 72 h, were fabricated. The responses to humidity for static and dynamic testing proved that both doping Ba into CeO2 and converting morphology into a nanowire can improve the humidity sensitivity. The resistance changes from 465 to 3.9 MΩ as the relative humidity (RH) increases from 25% to 88%, indicating promising applications of Ba-doped CeO2 nanowires in environmental monitoring.