This study examines the adsorption performance of MgO-biochar composites synthesized from oil palm empty fruit bunches of Oil Palm(EFBOP) for phosphate removal from aqueous solutions, highlighting their potential as a sustainable treatment approach. The composites were fabricated by incorporating MgO nanoparticles into KOH-activated biochar (KBc) at varying MgO:KBc ratios (1:5, 1:12.5, and 1:20). Comprehensive material characterization using FTIR, XRD, SEM, and BET analyses confirmed the successful integration of MgO onto the porous KBc matrix, resulting in enhanced surface area and the presence of key functional groups (Mg-OH, Mg-O) crucial for phosphate binding. Among the synthesized composites, the MgO:KBc composite with a 1:5 ratio exhibited the highest phosphate adsorption capacity of 9.31 mg/g, achieving an impressive 99.10 % removal efficiency from a 10 mg P/L solution. This performance significantly outperformed raw biochar and KBc, demonstrating a substantial synergistic effect between MgO nanoparticles and the activated biochar framework. Adsorption kinetics were best described by the pseudo-second-order model, indicating chemisorption as the dominant mechanism. Furthermore, the composite demonstrated excellent reusability, retaining 90.12 % of its phosphate removal efficiency after five consecutive adsorption-desorption cycles. The kinetic data was best represented by the pseudo-second-order model (R² > 0.99), indicating that chemisorption is the dominant rate-limiting step. Isotherm analysis using both Langmuir (R² = 0.9969) and Freundlich (R² = 0.9848) models suggested favorable phosphate adsorption. These study highlights the significant contribution of EFBOP-derived MgO-biochar composites as highly efficient adsorbents for mitigating phosphate pollution in wastewater, contributing to sustainable water resource management. © 2025 The Authors