The UV irradiation enhanced ZnO fiber sensors for organic gas detection at room temperature are reported in this paper. It has been well-known that the conductivity of ZnO fibers will increase when they are exposed to UV irradiation. However, it was found in this study that the trend of the conductivity increase under UV irradiation could be reversed if the organic gases adsorbed on the ZnO fiber surface. It was found that a linear relationship exists between the current response and the concentration of the organic gas. The results exhibited simple maneuverability for detecting parts per million concentration of organic gases at room temperature. The possible mechanism of photoconduction sensing for detecting an organic gas under UV light irradiation at room temperature is also discussed.