In this work, a Si/MoS2 heterojunction photodetector enhanced by hot electron injection through Fano resonance is developed. By preparing Au oligomers using capillary-assisted particle assembly (CAPA) on the silicon substrate with a nanohole array and covering few-layer MoS2 with Au electrodes on top of the oligomer structures, the Fano resonance couples with a Si/MoS2 heterojunction. With on-resonance excitation, Fano resonance generated many hot electrons on the surface of oligomers, and the hot electrons were injected into MoS2, providing an increased current in the photodetector under a bias voltage. The photodetectors exhibited a broadband photoresponse ranging from 450 to 1064 nm, and a large responsivity up to 52 A/W at a wavelength of 785 nm under a bias voltage of 3 V. The demonstrated Fano resonance-enhanced Si/MoS2 heterojunction photodetector provides a strategy to improve the photoresponsivity of two-dimensional materials-based photodetectors for optoelectronic applications in the field of visible and near-infrared detection.