Abstract: Solid oxide cells (SOCs), which include solid oxide fuel cells (SOFCs), symmetrical solid oxide cells (S-SOCs), and reversible solid oxide cells (R-SOCs), are considered key technologies for driving low-carbon and green revolution in the energy sector. Because of their clean, low-cost, and high-efficiency characteristics, SOCs have great potential for energy conversion and storage. However, the further development of SOC technologies faces challenges, such as a lack of long-term operational stability of the cell system, high material cost under high-temperature operating conditions, and limited catalytic effects at low temperatures. Recently, high-entropy materials (HEMs) have demonstrated excellent performance and wide application prospects in catalytic reactions, energy storage, supercapacitors, and other fields owing to their unique atomic arrangement and the four core effects (high mixed entropy stabilization effect, sluggish diffusion effect, lattice distortion effect, and “cocktail” effect). HEMs provide a new perspective for solving the aforementioned problems in the field of SOCs. This comprehensive review summarizes the applications of HEMs in the three fundamental components of SOCs: electrodes, electrolytes, and interconnects, focusing on the role of HEMs in enhancing catalytic activity and conductivity while mitigating harmful gas poisoning. In addition, this review proposes possible development directions for HEMs in SOCs based on the current research progress, providing valuable reference for high-entropy designs aimed at further enhancing the performance of SOCs.