This paper describes the equilibrium, kinetics and process mechanism studies on biosorption of lead ions fromaqueous solution using ‘Aspergillus niger’ in a batch process. The results indicate that biosorption of lead is influencedby various experimental parameters such as initial concentration of lead, amount of biomass used, variation in pH ofsolution and agitation speed. The lead uptake by biomass was quantitatively evaluated using sorption isotherms likeFreundlich and Langmuir isotherm. The results indicate that Langmuir isotherm model describes the present data verywell indicating favorable biosorption. Since the process follows pseudo second order kinetics, the mechanism ofbiosorption of lead by Aspergillus niger can be explained by shrinking core model.