Electrocatalytic nitrogen reduction reaction (NRR) is an appealing route for the sustainable NH₃ synthesis, while developing efficient and durable NRR catalysts remains at the heart of achieving high-efficiency N₂-to-NH₃ electrocatalysis. Herein, we rationally combine vacancy and interface engineering to design sulfur-deficient Bi₂S₃ nanoparticles decorated Ti₃C₂T_x-MXene as an effective NRR catalyst. The developed Bi₂S₃ nanoparticles decorated Ti₃C₂T_x-MXene (Bi₂S_3-x/Ti₃C₂T_x) naturally contained abundant S-vacancies and exhibited a dramatically boosted NRR activity with an NH₃ yield of 68.3 μg·h⁻¹·mg⁻¹ (−0.6 V) and a Faradaic efficiency of 22.5% (−0.4 V), far superior to pure Bi₂S₃ and Ti₃C₂T_x, and surpassing almost all ever reported Bi- and MXene-based NRR catalysts. Theoretical investigations unveiled that the exceptional NRR activity of Bi₂S_3-x/Ti₃C₂T_x stemmed from its dual-active-center system involving both S-vacancies and interfacial-Bi sites, which could synergistically promote N₂ adsorption and *N₂H formation to result in an energetic-favorable NRR process.