Perovskites have prevailed in the field of photovoltaics over the past several years thanks to their outstanding optoelectronic properties. Compared to threedimensional (3D) perovskites, the emerging two-dimensional (2D) Ruddlesden− Popper (RP) phase perovskites have demonstrated superior stability due to their hydrophobic organic capping ligands, which can protect the inside inorganic octahedrons against moisture. Meanwhile, RP perovskites broaden the family of 2D materials, enriching the building blocks for van der Waals heterostructures. Here, we first demonstrated a vertical heterojunction incorporating RP perovskite (C 6 H 5 C 2 H 4 NH 3 ) 2 PbBr 4 and MoS 2 . The heterojunction photodetector exhibits an extremely low dark current down to 0.1 pA, which can be attributed to the combining effect of the low carrier density in RP perovskites and the band structure of the heterojunction. The spatially resolved scanning photocurrent microscopy (SPCM) was carried out to confirm the charge transport mechanism and band alignment of the heterojunction. Moreover, the photodetector benefits from the heterojunction structure, leading to a high photoresponsivity (7.98 mA W −1 ). In addition, the device can be operated under a self-driven mode with a responsivity of 0.168 mA W −1 . Our work proves the compatibility of RP perovskites in van der Waals devices, promising a scalable pathway to further applications.