<p><i>Phragmites australis</i>, commonly known as the common reed, is a widely distributed perennial grass that thrives in various environmental conditions, including acidic, saline, and alkaline habitats. It adapts to a different soil textures, from fine clay to sandy loam. However, its rapid vegetative growth and high biomass production, leading to reduced biodiversity and diminished recreational value of riverbanks. Due to that, common reed biomass presents a valuable resource for synthesizing zero-valent iron nanoparticles, which have demonstrated effectiveness in pollutant remediation. Contaminated river sediments poses a significant environmental challenge, particularly due to the presence of toxic metals. Implementing stabilization techniques that incorporate inorganic amendments can help immobilize these metals and reduce their environmental impact. This study introduces a circular-economy-oriented strategy that simultaneously addresses two environmental issues: repurposing common reed biomass, as agro-industrial waste, for byosinthesis of iron nanoparticles and remediating metal-contaminated sediment from the same location. Sequential extraction and leaching tests were conducted to assess the effectiveness of the applied treatment. The results demonstrated that the mixtures were classified as non-hazardous waste, as the leached concentrations of metals remained below the maximum permissible limits set by the prescribed regulations, but still stay bound to reducible and oxidizable phase of the sediment, not so tightly bound within mineral structures. These findings highlight the potential of biosynthesized iron nanoparticles from common reed leaf extracts for remediating metal-contaminated sediments. Furthermore, the treated sediment may be repurposed for beneficial applications, contributing to environmentally responsible waste management and remediation strategies.</p>