Abstract Perovskites have showed significant potential for the application in photodetectors due to their outstanding electrical and optical properties. Integrating two-dimensional (2D) materials with perovskites can make full use of the high carrier mobility of 2D materials and strong light absorption of perovskite to realize excellent optoelectrical properties. Here, we demonstrate a photodetector based on the WTe₂/CsPbI₃ heterostructure. The quenching and the shortened lifetime of photoluminescence (PL) for CsPbI₃ perovskite confirms the efficient charge transfer at the WTe₂/CsPbI₃ heterojunction. After coupled with WTe₂, the photoresponsivity of the CsPbI₃ photodetector is improved by almost two orders of magnitude due to the high-gain photogating effect. The WTe₂/CsPbI₃ heterojunction photodetector reveals a large responsivity of 1157 A W⁻¹ and a high detectivity of 2.1 × 10¹³ Jones. The results pave the way for the development of high-performance optoelectronic devices based on 2D materials/perovskite heterojunctions.