Polyimide (PI), which have many remarkable features such as excellent mechanical strength, outstanding thermal stability, exceptional electric properties, etc, is a potential carrier for optoelectronic devices due to its abundant applications. However, because of chemical inertness and smooth surface that led to the growth of materials on this substrate being more complex than that on rigid substrate, thus, this report aims to emphasise the synthesis of ZnO NRs decorated with the Ag NPs on flexible substrate for photodetector application. In this study, we successfully synthesise ZnO NRs/Ag NPs on a flexible PI substrate by the hydrothermal method. The performance of our photodetector in visible region (395 nm) exhibits via the responsivity of the device, which recorded value of ca. 40.16 mA W−1 at 1.66 mW cm−2. With obtained results, our research can pave the way for future studies based on flexible optoelectronic devices.