The bioremoval potential of brown marine macroalga Padina pavonia for the uranium ions from aqueous solutions was studied under different experimental conditions with respect to the influences of pH, initial uranyl concentration, contact time, biomass dosage, and temperature of solution. Langmuir, Freundlich, Dubinin-Radushkevich, Flory-Huggins, and Brunauer-Emmett-Teller models were applied to describe the biosorption isotherm of uranium ions by P. pavonia biomass. Thermodynamic parameters such as biosorption enthalpy, entropy and free energy transition have been calculated. Biosorption from simulated artificial wastewater by P. pavonia was also investigated. Bioremoval efficiency and distribution coefficient of biomass, under the optimum biosorption conditions were calculated as 98 +/- 1% and 5257 +/- 312 mL/g, respectively. The Dubinin-Radushkevich isotherm model better fits the biosorption data and the experimental biosorption capacity was found to be 162 mg UO22+/g.