Abstract This work summarizes the preparation of two dimensional WO3 nanostructures by hydrothermal method and their NO2 sensing characterization in the ppb level (90-310 ppb). WO3 ultra-thin nanoplates with 100nm of lateral size and about 10nm of thickness were synthesized and characterized. Hydrothermal treatment (180°C, 48hours) was carried out on tungstic acid which obtained by direct precipitation of sodium tungstate dihydrate in hydrochloric acid. The morphology of the obtained WO3 was observed by SEM and TEM and their crystal structures were determined by X-ray diffraction (XRD). Thick films (∼ 5μm and 20μm) of the synthesized WO3 were prepared by screen-printing, the NO2 sensing characterizations of the sensors in the ppb level (90-310 ppb) were performed under different operating conditions (temperature from 200°C to 280°C and relative humidity from 0% to 100%). The sensitivity of the sensors, response and recovery times are reported and discussed.