Abstract: Image sensors are essential devices for acquiring visual information and are widely used in consumer electronics, industrial inspection, medical imaging, machine vision, and other fields. Although conventional silicon-based complementary metal-oxide-semiconductor (CMOS) image sensors are technologically mature in terms of pixel miniaturization, array scale, readout speed, and on-chip processing, their ability to meet emerging demands for extended spectral response, conformal sensing, and low-temperature fabrication over ultralarge areas remains constrained by the spectral absorption limit of silicon, optical losses introduced by color filters, and conventional wafer-based processing. Organic semiconductors offer tunable absorption spectra, relatively high absorption coefficients in targeted wavelength bands, low-temperature film formation, mechanical flexibility, and compatibility with large-area processing. Consequently, they have demonstrated considerable potential in visible and color imaging, near-infrared imaging, ultraviolet imaging, and indirect X-ray imaging. This review presents the device and pixel architectures of organic image sensors together with their multilevel performance metrics. Three integration routes are systematically examined: backplane-free or external-readout integration, thin-film transistor (TFT) active-matrix integration, and heterogeneous integration with CMOS/readout integrated circuits (ROICs). Their integration characteristics and applicable scenarios are compared, and representative applications are summarized. Existing studies indicate that the imaging performance of organic photosensitive layers is jointly governed by the operating bias, interfacial selectivity, pixel-node design, array uniformity, and compatibility with readout circuitry. In the near term, organic image sensors are more likely to complement mature silicon technologies than to replace them. Nevertheless, further improvements are required in array uniformity, long-term reliability, testing standardization, and manufacturing yield at scale.