The aquatic ecosystem is threatened globally by eutrophication due to ammonia nitrogen inputs from wastewater. Developing high-performance adsorbents with high removal efficiency and selectivity for ammonia nitrogen is pivotal to ecological equilibrium. Here, the removal of ammonia nitrogen by a combined process of Co-based Prussian blue (NaCo-PBA) and coagulants was studied for the first time. The maximum adsorptive capacity of ammonia nitrogen by NaCo-PBA was 52.72 mg/g, and the removal reached 99 %. Compared with traditional adsorbents, NaCo-PBA showed high adsorption amounts (9–42 times). Most importantly, NaCo-PBA exhibited selectivity in complex systems and its adsorption quantity reached 42.6 mg/g in real domestic wastewater, compared to 4.7 mg/g for commercial adsorbent. NaCo-PBA was used in the coagulation and co-adsorption process to facilitate the separation of multiple contaminants in water. It is reasonable to believe that the collaboration between NaCo-PBA with special structure and coagulation will bring a new perspective to nitrogen removal in complex systems.