With the increasing demand for sustainable energy technologies, ionic thermocells are receiving more and more attention due to their potential to correct low-grade heat by directly converting thermal energy into electrical energy. Among the key performance indicators, the effective thermal conductivity (κ_eff) plays a crucial role in maintaining internal temperature gradients and enhancing overall energy conversion efficiency of thermocells. However, compared with the extensively studied thermopower (S_tg) and electrical conductivity (σ), κ_eff has received less systematic attention. This review summarizes recent advances in the regulation of thermal conductivity in ionic thermocells, focusing on its crucial role in thermoelectric performance. We discuss the influences of electrode materials, electrolyte compositions, and device architectures on heat transport, and highlight representative strategies involving materials engineering and structural design to optimize the synergy between thermal conduction and ionic conduction. Finally, we outline future directions such as material optimization, interface engineering, and improved thermal characterization techniques to promote the development of next-generation high-performance thermocells.