CsPbCl3 perovskite is attracting increasing interest in ultraviolet (UV) detection due to its optical band gap and superior intrinsic optoelectronic properties. In this study, a novel one-step magnetron sputtering technique was applied for fabricating CsPbCl3 polycrystalline films on flexible plastic substrates with interdigitated contacts. The photoconductive response of 500 nm and 1 µm thick films to pulsed ultraviolet (UV) light in the 0.1–100 Hz frequency range and intensity of 10–500 W/m2 was tested at room temperature. The experimental results demonstrated the good performances of the CsPbCl3 films in terms of signal stability, fast response to transient signal, detectivity, light dynamic range, and dark current noise for the photodetection of pulsed UV light.