Acacia dealbata, an invasive species in Portugal, produces large amounts of residual biomass during control operations, thereby presenting challenges and opportunities for sustainable valorization. Heavy metal contamination, including zinc (Zn), remains a critical environmental challenge due to its widespread industrial release and potential ecotoxicological impacts. This study explores the potential use of A. dealbata biomass as a biosorbent for zinc removal from aqueous solutions, comparing the performance of natural biomass and A. dealbata charcoal fines. Adsorption isotherms, kinetics, and surface characterizations were conducted to evaluate their physicochemical properties and sorption efficiency. The A. dealbata charcoal fines exhibited a significantly higher specific surface area (33 m² g⁻¹) and total pore volume (0.030 cm³ g⁻¹) compared with the untreated biomass (1.4 m² g⁻¹ and 0.004 cm³ g⁻¹, respectively). Despite these structural differences, both materials demonstrated similar maximum adsorption capacities (23.36 and 23.79 mg g⁻¹ for natural and charcoal fines, respectively). These results indicate that untreated A. dealbata biomass can perform as a biosorbent comparably to its carbonized form, representing a simple, low-cost, and sustainable alternative for heavy metal removal, offering a low-energy and sustainable alternative for Zn remediation.