An ethanol gas sensor with enhanced sensor response was fabricated using Ni-doped SnO 2 nanorods, synthesized via a simple hydrothermal method. It was found that the response (R= R 0/R g) of a 5.0 mol% Ni-doped SnO 2 (5.0 Ni: SnO 2) nanorod sensor was 1.4× 10 4 for 1000 ppm C 2 H 5 OH gas, which is about 13 times higher than that of pure SnO 2 nanorods,(1.1× 10 3) at the operating temperature of 450 C. Moreover, for 50 ppm C 2 H 5 OH gas, the 5.0 Ni: SnO 2 nanorod sensor still recorded a significant response reading, namely 2.0× 10 3 with a response time of 30 s and recovery time of 10 min. To investigate the effect of Ni dopant (0.5–5.0 mol%) on SnO 2 nanorods, structural characterizations were demonstrated using field emission scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction (XRD) analysis, x-ray photoelectron spectroscopy and an ultraviolet–visible spectrometer. XRD results confirmed that all the samples consisted of tetragonal-shaped rutile SnO 2 nanorods. It was found that the average diameter and length of the nanorods formed in 5.0 Ni: SnO 2 were four times smaller (∼ 6 and∼ 35 nm, respectively) than those of the nanorods formed in pure SnO 2 (∼ 25 and 150 nm). Interestingly, both samples had the same aspect ratio,∼ 6. It is proposed that the high response of the 5.0 Ni: SnO 2 nanorod sensor can be attributed to the particle size, which causes an increase in the thickness of the charge depletion layer, and the presence of oxygen vacancies within the matrix of SnO 2 nanorods.