This study evaluated the impact of ibuprofen (IBP) on nitrogen and phosphorus removal in a novel anaerobic/oxic/anoxic (AOA) system operated at 10–15 °C with influent IBP concentrations of 0–6 mg/L. Reactor performance, sludge properties, microbial activity, and community composition were monitored to elucidate the underlying mechanisms. Increasing IBP concentrations progressively impaired pollutant and nutrient removal. IBP exposure decreased mixed-liquor suspended solids, organic content, and sludge settleability, but markedly increased extracellular polymeric substances (EPS); at 6 mg/L, total EPS, protein, and polysaccharide contents reached 95.8～99.7, 64.5～66.1, and 31.4～34.2 mg/g, respectively. The specific oxygen uptake rate fell to 34.2 mg/(g·VSS·h), whereas reactive oxygen species and lactate dehydrogenase activities rose, indicating oxidative stress and diminished metabolic activity. High IBP levels also reduced the relative abundances of Proteobacteria and Acidobacteriota. These findings improve understanding of IBP behaviour in low-temperature wastewater and provide guidance for sustaining efficient nutrient removal in AOA systems.