TiO2 nanocrystals were prepared by sol–gel/solvothermal processing and modified by the addition of W precursor before the solvothermal step. The W: Ti nominal atomic ratio (RW) was fixed to 0.16 and 0.64. Surface modification of TiO2 occurred for RW = 0.16 while for RW = 0.64 nanocomposites with WO3 nanocrystals were obtained after heat-treatment at 500 °C. Pure TiO2 proved to be very poorly performing in acetone sensing in all the operating conditions. Instead, the addition of both W concentrations largely enhanced the sensor response. It ranged over two orders of magnitude of conductance variation for all the tested concentrations at as low as 200 °C operating temperature. The results showed that it is possible to enhance the performance of an otherwise almost inactive oxide like TiO2 by proper combination with another more active oxide like WO3.