WO3 and Cr–WO3 powders were prepared by sol–gel process, with Cr:W atomic concentration ranging from 2% to 8.8%. WCl6 was used as W precursor and reacted with methanol in presence of acetyacetone as stabilizer. The required amount of Cr 2-ethylhexanoate was then added to the resulting solution, which was subsequently dried. The resulting powder was heat-treated at temperatures ranging from 200 to 700 °C. With increasing the Cr concentration, the samples heat-treated at 500 °C contained an increasing amount of the additional phase Cr2WO6, as evidenced by X-ray diffraction and Transmission Electron Microscopy. The sensing tests toward ammonia gas, from 50 to 500 ppm showed that, up to 5% concentration, Cr addition lowered the best operating temperatures and/or enhanced the response with respect to pure WO3, then the response remarkably decayed. DFT modeling showed that Cr(III …