<p>Solid-state lithium-sulfur batteries retain high theoretical energy density and low cost of sulfur while eliminating safety issues associated with liquid electrolytes, such as leakage and flammability. More importantly, most solid electrolytes can reduce the shuttle effect caused by the dissolution of polysulfides, offering great potential to enhance both the safety and long-term performance of lithium-sulfur batteries. However, interfacial issues caused by poor solid–solid contact and inadequate electrode wettability have become critical bottlenecks for the practical application of solid-state lithium-sulfur batteries. In situ polymerization offers a promising solution by enabling polymerization after monomers infiltration, retaining polymer strength while filling voids and enhancing electrode-electrolyte integration. Here, we review recent advances in in situ polymerization for Li-S batteries, analyzing the operational principles and electrochemical merits. We further highlight the persistent challenges of in situ polymerized materials and propose future prospects for multifunctional polymer solid-state electrolytes.</p>