The escalating concentration of phosphorus in wastewater, primarily from industrial and agricultural activities, poses a critical environmental threat. This surplus phosphorus is a major driver of eutrophication, leading to severe adverse impacts on aquatic ecosystems, including oxygen depletion, biodiversity loss, and overall water quality degradation, ultimately affecting human health. Consequently, developing effective and sustainable strategies for phosphorus removal from wastewater before its environmental discharge is an imperative research priority. This study aimed to engineer an efficient and environmentally benign phosphorus adsorbent by valorizing locally abundant agricultural waste: bamboo waste. The bamboo waste was converted into biochar via controlled pyrolysis at 500, 600, and 700 °C for 2 hours. Subsequently, the biochar's surface was chemically modified with chitosan, a natural biopolymer, to enhance its phosphate adsorption efficiency. Adsorption performance was rigorously evaluated using synthetic wastewater with a phosphate concentration of 20 mg PO43-/L. Findings revealed that the chitosan-modified bamboo biochar pyrolyzed at an optimal 600 °C exhibited the most promising characteristics. This adsorbent demonstrated a significant 30.59% increase in iodine adsorption capacity compared to unmodified biochar, indicating enhanced surface area and porosity. Crucially, it achieved the highest phosphate adsorption capacity of 0.76 mg/g, representing a substantial 17.71% increase over samples produced at other temperatures. This study confirms the remarkable potential of chitosan-modified bamboo biochar as a sustainable adsorbent material for advanced phosphorus management in wastewater treatment. This innovative approach not only contributes to efficient wastewater purification but also offers a valuable pathway for upcycling agricultural waste, aligning with principles of sustainable materials and circular economy, with potential for future applications in adsorbing other pollutants.