WO3 film sensors with various crystalline morphologies have been investigated for highly sensitive detection of dilute NO2. Four types of WO3 particles, spherical, disk, cuboid, and hexagonal, were prepared by pyrolysis (spherical), precipitation method (disk), and hydrothermal synthesis under different conditions (cuboid and hexagonal). WO3 film sensors were fabricated on Au comb-type microelectrodes by suspension dropping using the various WO3 powders obtained, and their sensor properties to dilute NO2 were investigated at 200°C. The cuboid WO3 film sensor showed the best response-recovery property with 90% response and 90% recovery times of 1.3 and 0.9 min to 0.05 ppm NO2 at 200°C, respectively. The hexagonal WO3 film sensor showed extremely high sensitivity of 41.1 to 0.01 ppm NO2 at 200°C. The sensor performance suggested the possibility of environmental monitoring of dilute NO2 using WO3 film sensors.