Metal-halide perovskite narrowband photodetectors offer a low-cost opportunity to detect specific signals covering a broad spectrum directly. However, the thickness of charge collection narrowing mechanism photodetectors increases recombination, resulting in performance bottlenecks. Here, we demonstrate amplified narrowband photodetectors that combine perovskite single-crystal absorbers and organic multiplication layers. The separation of the multiplication layer controls the density of trap states while amplifying the response of conventional narrowband photodetectors by more than 215 times. The carrier dynamics were characterized by ultrafast measurement, thus verifying the mechanism of response amplification. By analyzing multiplication with different trap states energy levels under charge injection, it is shown that dopants have a wide selection space, providing a feasible path for high-performance narrowband photodetectors. As a result, the external quantum efficiency of 2259% with a 38-nanometer full width at half maximum and the specific detectivity of 4.84 × 10 12 Jones was obtained at 825 nanometers. Last, we demonstrated the anti-interference signal acquisition capability of our photodetector.