The Cr-doped CeO2 nanomaterials were prepared by a simple hydrothermal method. Morphological analysis revealed that Cr doping altered the morphology and size of the CeO2 particles. Gas sensing tests results showed that Cr/Ce-2 has the highest response (Ra/Rg = 15.6 @ 10 ppm), which was 12.58 times higher than that of the pure CeO2 sensor. Furthermore, the optimal operating temperature was reduced from 210 °C to 170 °C. The Cr/Ce-2 sensor also displayed outstanding repeatability and gas selectivity. The improved gas sensing performance of the Cr-doped CeO2 sensor can be attributed to its smaller grain size and higher porosity compared to pure CeO2. In addition, oxygen vacancies played a pivotal role in improving the gas-sensing performance. The present work provides a new CeO2-based gas-sensitive material for the detection of n-butanol.