This paper presents the acetone sensing characteristics of Si-doped (1 at.%) tungsten oxide thin films prepared by glancing angle dc magnetron sputtering. The performance of Si-doped WO ₃ sensors in the concentration range of 0.04-3.8 ppm at operating temperatures of 150 °C-425 °C has been investigated. Doping of the tungsten oxide film with Si significantly decreases the limit of detection of acetone compared with the pure WO ₃ sensors reported in the literature. The gas sensor's response (S) to acetone was defined as the resistance ratio S = R _air /R _gas , where R _air and R _gas are the electrical resistances for the sensor in air and in gas, respectively. The maximum response measured in this experiment was S = 40.5. Such response was measured in the presence of 3.8 ppm of acetone at an operating temperature of 425 °C using a Si-doped (1 at.%) WO ₃ thin film deposited at 300 °C and annealed at 300 °C for 4 h in air. The films phase composition, microstructure, and surface topography have been assessed by X-ray diffraction, scanning electron microscope, atomic force microscope, and energy dispersive X-ray spectroscopy methods.