The study of economic, green, and efficient sewage treatment methods has been a major challenge for the water treatment industry due to the complex nature of wastewater and the increasing demand for clean water supply. Layered double hydroxides (LDHs) are a kind of anionic clay with strong anion exchange capacity, good adjustability, high thermal stability, and rich active sites. As a class of adsorption materials, it has been widely used to adsorb various pollutants in wastewater and shows excellent removal performance. However, the defects in functional groups and structural components severely limit the adsorption performance and application range of pristine LDHs. The functionalization of LDHs with different modification strategies can significantly enhance the pollutant adsorption capacity and selectivity, stability, recyclability, as well as application scope. Based on the optimization of the performance of LDHs in the treatment of pollutants in wastewater, this review focuses on the commonly used functional modification strategies of LDHs, such as intercalation, surface modification, calcination, composite assembly, entrapment, and membrane preparation. The intercalation and surface modification treatment increases the number of special functional groups and promotes the selective adsorption of LDHs for target pollutants. The calcination treatment increases the adsorption efficiency of LDHs for anionic pollutants. And the efficient separation and recovery of LDHs can be realized by other methods, such as composite assembly, entrapment, and membrane preparation. Subsequently, the interaction mechanism between functionalized LDHs and various inorganic non-metallic anions, heavy metal ions, organic dyes, and antibiotic pollutants in wastewater was summarized. In addition, the regeneration methods of functionalized LDHs were also described. Finally, the advantages and the possible obstacles of functionalized LDH adsorbents in the next study were briefly proposed, and its broad application prospects were provided.