Tetracycline (TC), a widely used antibiotic, persists in aquatic environments due to its chemical stability, bioaccumulation potential, and role in promoting antimicrobial resistance, posing significant ecological and public health risks. To address the pressing need for effective wastewater treatment technologies, a cobalt nanoparticle-embedded boron nitride nanocomposite (Co/BN) was developed for efficient peroxymonosulfate (PMS) activation. Among the synthesized catalysts, Co/BN-1 exhibited outstanding performance, achieving near-complete TC degradation within 5 min under mild conditions, along with excellent stability and reusability over four consecutive cycles, accompanied by minimal cobalt leaching. Mechanistic studies combining radical scavenging assays and LC-MS analysis revealed the involvement of both radical species (SO₄⁻ and OH) and non-radical pathways (¹O₂), highlighting a synergistic effect between Co nanoparticles and the BN matrix. This work demonstrates the feasibility of Co/BN composites as highly efficient, stable, and eco-friendly catalysts for sulfate radical-based advanced oxidation processes (SR-AOPs), providing a promising strategy for the rapid and sustainable removal of antibiotic pollutants from water systems.