All-solid-state lithium batteries using nonflammable inorganic solid electrolytes can completely eliminate the safety issues, such as leakage and combustion. Moreover, energy densities can be improved significantly using transition metal sulfide electrodes and metallic lithium in all-solid-state lithium batteries owing to their high theoretical specific capacity and excellent interfacial compatibility with sulfide solid electrolytes. In this work, nickel sulfide anchored carbon nanotube (NiS–CNT) nanocomposites were successfully synthesized by a facile hydrothermal method. The very small NiS particle size with a distribution of 5–10 nm as well as the presence of multi-walled carbon nanotubes not only enhance the ionic/electronic conduction but also alleviate the volume changes, which endow the NiS–CNT based all-solid-state lithium batteries with superior rate capability and excellent cycling performances. Typically, Li/75% Li₂S–24% P₂S₅–1% P₂O₅/Li₁₀GeP₂S₁₂/NiS–CNT all-solid-state lithium batteries delivered a high reversible capacity of 515 mA h g⁻¹ after 30 cycles at a current density of 0.1 A g⁻¹. Even after increasing the current density to 1.0 A g⁻¹, the all-solid-state lithium batteries still maintain a stable discharge capacity of 170 mA h g⁻¹ after 150 cycles. Moreover, the conversion reaction mechanism of the NiS–CNT nanocomposites in all-solid-state lithium batteries was investigated by ex situ XRD measurements.