Adsorption of fluoride (F) by Aspergillus and Ca-pretreated Aspergillus biomass was conducted in an aqueous batch system and the maximum F adsorption capacities were found to be 8.09 mg/g (at pH 10) and 4.80 mg/g (at pH 8) respectively. For both the Aspergillus and Ca-pretreated Aspergillus adsorbents, the equilibrium isotherm fitted with the Freundlich isotherm and the adsorption kinetics obeyed the pseudo-second order equation. Thermodynamic analysis indicated that the adsorption process was exothermic and spontaneous for both adsorbents. Fourier transform infrared analysis of Aspergillus indicated the existence of potential fluoride-capturing functional groups. © 2013 The International Society for Fluoride Research Inc.