Antimony selenide (Sb 2 Se 3 ) semiconductor with a narrow band gap is regarded as an ideal candidate for the next-generation broadband photodetectors. However, the photodetectors based on the binary Sb 2 Se 3 semiconductor suffer from low responsivity (R λ ) and external quantum efficiency due to the intrinsic low electrical conductivity. To address the issue, we introduce a low-valence Ni cation (Ni 2+ ) into the binary Sb 2 Se 3 ((Sb 1−x Ni x ) 2 Se 3 ) nanorods synthesized by a facile hot-injection process. With increasing Ni-doping concentration, the (Sb 1−x Ni x ) 2 Se 3 nanorods exhibit a significant increase of electrical conductivity from 4.983 × 10 −5 to 4.011 × 10 −4 Ω −1 m −1 . The photodetector based on (Sb 0.995 Ni 0.005 ) 2 Se 3 nanorod film exhibits an excellent responsivity of 18.9 mA/W under white light illumination of 45 mW/cm 2 at an applied bias voltage of 3 V, which is an approximately 19fold higher than that of the pristine Sb 2 Se 3 nanorod photodetector. Moreover, the density functional theory calculation has demonstrated that the Ni 2+ doped into Sb 2 Se 3 will preferentially occupy the Sb site and introduce a shallow energy level of acceptor, resulting in the enhancement of electrical conductivity, which is consistent with the experimental result. Therefore, the work proves the substitution of Sb site with a low-valence metal cation into Sb 2 Se 3 is an effective strategy to improve the performance of the Sb 2 Se 3 -based photodetector.