Abstract: Cobalt-based layered double hydroxide (Co-LDHs) composites are constructed through the incorporation of redox-active cobalt species (Co²⁺/Co³⁺) into the two-dimensional framework of layered double hydroxides. These materials have garnered significant research interest as peroxymonosulfate activators in advanced oxidation processes owing to their distinctive layered structure, anion exchange capacity, and structural memory effect. A systematic review of recent advances in Co-LDHs applications for environmental pollutant removal is presented herein. Three predominant synthesis methodologies—coprecipitation, hydrothermal synthesis, and template-assisted fabrication—are comprehensively delineated. Emphasis is placed on the modification strategies, including metal doping and carrier substrate loading, along with morphological engineering (e.g., sheet-like architectures, porous frameworks, and core–shell structures), whose mechanisms for enhancing catalytic performance are critically discussed. The influences of key environmental parameters on pollutant degradation efficiency are systematically examined. Furthermore, the mechanisms underlying peroxymonosulfate activation and contaminant degradation are elucidated from multiple analytical perspectives. Finally, prospective pathways for the optimization of Co-LDHs-based peroxymonosulfate activation systems and potential research directions are proposed.