Abstract Polycrystalline CuInS 2 thin films were deposited on glass substrates using a novel solution-based continuous flow microreactor process for the first time. A series of analysis was performed to characterize the CuInS 2 thin films using UV–visible spectrophotometer, scanning electron microscope, X-ray diffraction spectrometer, and X-ray photoelectron spectroscopy. The estimated optical band gaps of CuInS 2 thin films were in the range of 1.52–1.60 eV. The structural and chemical binding information indicated that CuInS 2 thin films with a tetragonal chalcopyrite structure were successfully deposited. Dense film with a thickness around 1 μm could be obtained with a 5 min deposition time. This study demonstrates the solution-based continuous flow microreactor process is a promising low cost alternative for thin film PV manufacturing.