Magnetic [email protected] oxide nanocatalyst ([email protected]), a composite material comprising powdered activated carbon (PAC) and ferroferric oxide nanocatalyst (FONC), was prepared using chemical co-precipitation. In this study, we evaluated the performance and complete pathway of tetracycline (TC) degradation in a [email protected]/H₂O₂ system. Moreover, the toxicity of TC and its intermediates was estimated. TC degradation in the [email protected]/H₂O₂ system followed pseudo-first-order kinetics, and the TC removal efficiency reached 97% in 120 min (TC₀ = 150 ppm). The electron spin resonance (ESR) analysis and free radical quenching experiments indicated the generation of •OH and HO₂• during the reaction. The investigation of the reaction mechanisms revealed the complementary performances between [email protected] adsorption and heterogeneous Fenton-like reaction in the TC degradation process. The stability of [email protected] recycling was also measured by multiple cycles of reactions, and the TC removal rate still reached 85.8% after nine cycles. In addition, the superparamagnetism and negligible iron leaching of the [email protected]/H₂O₂ system represented significant improvements relative to PAC and the conventional homogeneous Fenton process, making it a promising composite for applications in advanced oxidation processes.