Flexible photodetectors are fundamental components for developing wearable systems, which can be widely used for medical detection, environmental monitoring and flexible imaging. However, compared with 3D materials, low-dimensional materials have degraded performance, a key challenge for current flexible photodetectors. Here, a high-performance broadband photodetector has been proposed and fabricated. By combining the high mobility of graphene (Gr) with the strong light–matter interactions of single-walled carbon nanotubes (SWCNTs) and molybdenum disulfide (MoS2), the flexible photodetector exhibits a greatly improved photoresponse covering the visible to near-infrared range. Additionally, a thin layer of gadolinium iron garnet (Gd3Fe5O12, GdlG) film is introduced to improve the interface of the double van der Waals heterojunctions to reduce the dark current. The SWCNT/GdIG/Gr/GdIG/MoS2flexible photodetector exhibits a high photoresponsivity of 47.375 A/W and a high detectivity of 1.952 × 1012Jones at 450 nm, a high photoresponsivity of 109.311 A/W and a high detectivity of 4.504 × 1012Jones at 1080 nm, and good mechanical stability at room temperature. This work demonstrates the good capacity of GdIG-assisted double van der Waals heterojunctions on flexible substrates and provides a new solution for constructing high-performance flexible photodetectors.