Response surface methodology (RSM) employing 5-level Box-Behnken design was used to optimize the biosorption of cerium(III) onto biowaste materials of animal and plant origin viz. prawn carapace (PC) and corn style (CS). Various process parameters viz. pH (A: 3.0-9.0), biomass dosage (B: 0.05-0.35 g/L), initial metal concentration (C: 50-350 mg/L), contact time (D: 2-6 h) and temperature (E: 20-60 °C) were chosen for optimization. A log transformation was suggested by the Box-Cox plot in the present case. A low p-value of {\textless}0.0001 validated the significance of the model. Maximum Ce(III) uptake of 218.3 mg/g for PC and 180.2 mg/g for CS was noted under optimum conditions. Among the equilibrium isotherms, Freundlich model was found to be the best fitted one suggesting a heterogeneous mode of biosorption on PC whereas Langmuir model showed the best fit suggesting homogeneous mode of cerium biosorption on CS. This was further confirmed by scanning electron microscopy (SEM). Kinetic studies showed better applicability of pseudo-first order model suggesting physisorption as phenomena underlying the process. Film-diffusion was suggested by the non-linearity of the Boyd plot. Thermodynamic studies showed that the process was endothermic and spontaneous. FTIR analysis confirmed a major involvement of the participation of amide, amines, ketones and primary alcohol groups during Ce(III) biosorption. EDAX analysis confirmed the major participation of carbon group during Ce(III) biosorption. This was the first report on parameter optimization of Ce(III) biosorption onto biowaste materials using 5-level Box-Behnken experimental design which might be helpful for the recovery of Ce(III) from aqueous environment.