Molybdenum disulfide (MoS₂) has received great interest as an anode material for sodium-ion batteries (SIBs) because of its appealing theoretical capacity. However, its low reaction kinetics and poor cycling stability severely hinder its widespread application. Herein, we outline a simple method for fabricating a series of ultra-thin MoS₂/carbon composites with different S-vacancy concentrations as efficient anodes for SIBs. The sample with an optimized S-vacancy concentration showed remarkable rate performance (276 mAh/g at a current density of 5 A/g) and high reversible capacity with exceptional stability (473 mAh/g at 1 A/g after 100 cycles). The Na⁺ storage kinetics results, combined with theoretical calculations, suggested that a 12.5 ∼ 18.75 % S-vacancy concentration (corresponding to S atoms) in MoS₂ can greatly promote Na⁺ insertion and alleviate structural changes, thus enhancing the reversible capacity, reaction kinetics, and stability of the anode.