Display omitted •We investigated the sensing behaviors of ZnO-SnO2 core-shell NWs, with the shell layer being deposited by ALD.•We obtained high sensor responses at 1 ppm of 18.24, 14.94, and 16.46, respectively, to CO, C7H8, and C6H6 gases.•The main sensing mechanism was related to the radial modulation effect as well as the volume fraction of the shell to the total volume of core-shell nanowires. ZnO-SnO2 core-shell nanowires (C-S NWs) with different shell thicknesses (0–120 nm) were prepared and their sensing behavior was systematically studied. ZnO-SnO2 C-S NWs were prepared using a two-step synthesis procedure, where core ZnO NWs were synthesized by a vapor-liquid-solid growth technique, and subsequently these cores were coated with SnO2 shell layers by using an advanced atomic layer deposition technique. The sensors were exposed to 10-ppm CO, C6H6, and C7H8 gases at an optimal working temperature. The shell thickness was optimized to be 40 nm, for which the sensor revealed the highest sensitivity and fastest dynamics to the above-mentioned gases. The sensing mechanism was discussed in detail and the dominant mechanism was related to the radial modulation effect as well as the volume fraction of the shell to the total volume of C-S NWs.