Abstract: The biosorption of Cd (II) ions from the aqueous solutions by A. nidulans strain isolated from contaminated soil was studied in batch system. The effect of pH (3, 4, 5 and 6), temperature (25, 30, 35, 40 and 45ºC) initial concentration (100 – 500 mg/ L) of Cd (II) ions on biosorption were investigated. The maximum biosorption capacity of A. nidulans was 258 mg/L at 350 mg/L of Cd (II) ions. The experimental results suggest that the second – order equation is the most appropriate equation to predict the biosorption capacity by A. nidulans. Biosorption equilibrium data was best described by Langmuir isotherm model followed by Freundlich model. The free energy change (∆G°) obtained for the biosorption of Cd (II) ions at the temperature of 298, 303, 308, 313 and 318 K was – 633, - 644, - 655, - 665 and – 676 by the fungal biomass at pH – 3. The high negative value of change in Gibbs free energy indicates the spontaneity and feasibility of the biosorption of Cd (II) by kJ/mol by A. nidulans.