Abstract The newly emerged 2D materials heterostructures, including layered and nonlayered structures, are regarded as the building blocks for future high performance optoelectronic devices. However, it still remains a great challenge to directly synthesize 2D heterostructures for realizing broadband detection in photodetectors. In this work, the growth of vertically stacked inorganic molecular Sb 2 O 3 /monolayer MoS 2 heterostructures through a two‐step chemical vapor deposition method is demonstrated, and high performance ultraviolet/near‐infrared photodetectors based on the achieved heterostructures are further developed. Excellent responsivity of 5.3 × 10 4 A W −1 and detectivity of 2.0 × 10 15 Jones are obtained under 457 nm illumination. Additionally, the photodetection range can be extended to near‐infrared region. Maximum responsivity of 7.8 A W −1 , detectivity of 3.4 × 10 11 Jones, and fast response speed (<60 ms) are obtained under 1064 nm laser illumination at room temperature, which is far superior to those of the previously reported ultra‐thin 2D van de Waals heterostructures. The inorganic molecular Sb 2 O 3 /monolayer MoS 2 heterostructures enrich the family of 2D materials heterostructures, showing potential applications in high performance functional electronics and optoelectronics.