Lithium sulfur (Li–S) batteries, as promising alternatives to lithium ion batteries (LIBs), are drawing significant attention owing to their high theoretical capacity and energy density. However, the sluggish reaction kinetics and poor cycling stability have remained a great challenge, hindering the practical application of Li–S batteries. Herein, sulfur–cobalt sulfide nanocomposites with tunable sulfur content were synthesized via a facile one-pot refluxing method towards enhanced reaction kinetics for Li–S batteries. Uniform distribution of sulfur and cobalt sulfide at the nanoscale was achieved in the composites. The sulfur–cobalt sulfide nanocomposites delivered higher specific capacities and significantly enhanced rate performance compared to bulk sulfur cathode. The significant performance improvement is in great part due to the formation of sulfur nanoparticles and greatly improved electrical conductivity of the nanocomposites, which would result in shortened mass diffusion pathway and enhanced charge-transfer ability, thereby inducing accelerated electrode reaction kinetics.