This study determined the biosorption capacity of algal waste, obtained through agar extraction from Gracilaria tenuistipitata, a common red seaweed in the Philippines and potential biosorbent, on Zn2+ ions. Agar was extracted from the seaweed and characterized through Fourier-transform infrared spectroscopy (FT-IR). The algal waste was then subjected to a biosorption study involving various Zn2+ standards. Atomic absorption spectroscopy (AAS) and FT-IR were employed to evaluate sorption processes. Biosorption data was analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms which yielded  values of 0.9680, 0.8103, and 0.5254, respectively. The Langmuir ( ), Freundlich ( ), and D-R ( ) constants garnered were 0.0231 L/mg, 0.9829 mg/g, and 2.159  10-6 mol2 J-2 respectively, qualifying the adsorption of Zn2+ ions onto the algal waste as a favorable and physical process. FT-IR spectra analysis suggests that carboxylic acid and amide groups are involved in biosorption, possibly an ion-exchange process taking place for the uptake of Zn2+ ions. It was concluded that G. tenuistipitata waste is a promising biosorbent for Zn2+ ions. Performing the biosorption procedure in triplicates and the inclusion of kinetic studies are recommended to improve and ensure the accuracy in determining biosorption capacity and optimization in future studies.