The third, fourth, fifth, and sixth instars of the cotton leaf worm Spodoptera littoralis (Boisduval, 1833) were reared on castor bean leaves Ricinus communis (Linnaeus, 1753) treated with cadmium 100 mg CdCl2/kg, using the dipping method, to evaluate the effect of cadmium (Cd) on nutritional indices. It was observed that the consumption index was significantly decreased at all the studied instars except for the third instar. The absorptive capacity, in terms of approximate digestibility, was significantly decreased at the sixth instar. The food utilization efficiencies, in terms of the conversion of ingested and digested food (ECD) to biomass, were significantly decreased at both fourth and fifth instars. Moreover, the ECD was significantly decreased at the sixth instar. The growth rate decreased at the different studied instars except for the sixth instar.