To improve lithium–sulfur (Li–S) battery performance, a new interlayer film of embedded palladium cobalt (Pd3Co) particles is developed. Pd3Co particles on multi-walled carbon nanotubes (MWCNTs) are synthesized by using a modified polyol method. The synthesis of Pd3Co on MWCNTs is confirmed by X-ray diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The interlayer film is prepared through a filtration method using these powders. Li–S batteries with this interlayer have electrochemical properties superior to those with an MWCNT interlayer (0.2, 0.5, and 2.0 C-rates). At 0.2 and 0.5 C-rates, Pd3Co/MWCNT-interlayer cell achieves a better performance than MWCNT-interlayer cell during 200 cycles. In addition, there is a definite performance difference for 2.0 C-rate during 300 cycles. The discharge capacities for the first and 300 cycles for the MWCNT-interlayer cell are 869 mAh g−1 and 525 mAh g−1, respectively, whereas those for a Pd3Co/MWCNT-interlayer cell are 953 mAh g−1 and 752 mAh g−1, respectively. These improvements are resulted from the catalytic role of Pd3Co, which assists the reaction of polysulfide formation/deformation.