Portable electrical devices have become integral to our daily lives, with many being powered by rechargeable batteries. The increasing demand for such batteries has prompted a search for alternative options. Among these alternatives, sodium-ion batteries (SIBs) stand out as promising candidates because of their operational similarity to lithium-ion batteries and cost efficiency. Despite the presence of some commercial SIB products, their overall performance falls short of meeting the requirements for large-scale manufacturing. A critical factor influencing the performance of SIBs is the cathode material. Recently, a novel concept involving high entropy has been introduced for use as a cathode material for SIBs. This review begins by introducing the high-entropy concept and then explores the methods used to synthesize cathode materials such as sodium layered oxides, Prussian blue analogs, and NASICON for SIBs. This review also presents state-of-the-art progress in these three types of materials. In the Conclusions section, we outline perspectives for high-entropy materials (HEMs). This comprehensive review aims to serve as a reference for studying HEMs in the context of SIBs.