Four 3,5-pyrazolidinedione derivatives namely, 4-(4`-chlorobenzylidene)-1-phenylpyrazolidine- 3,5-dione (1), 4-(4`-nitrobenzylidene)-1-phenylpyrazolidine-3,5-dione (2), 2'-(p-chlorophenyl)-1-phenyl-3,5-dioxo-1,2,3,5 tetrahydrospiropyrazole-4,3' oxirane (3) and 2'-(p-nitrorophenyl)-1-phenyl-3,5-dioxo-1,2,3,5 tetrahydrospiropyrazole-4,3' oxirane (4) were prepared in pure state and bioassayed against 2nd and 4th instars larvae of cotton leaf worm, Spodoptera littoralis (Boised) (Lepidoptera: Noctuidae) using feeding and dipping bioassay. The results of bioassays indicated that title compounds exhibited satisfactory insecticidal activities. Among those, compound (1) exhibited the highest insecticidal activities against 2nd instar larvae, with LC50s 3.23 and 0.619 mgL-1 for feeding, and 36.04 and 28.69 mgL-1 for dipping, after 48 and 72 h treatment. According to the toxicity index the compound (1) showed the highest larvicidal activity against 4th instar larvae with LC50s 141.33 and 76.12 mgL-1 for feeding larvae, and 26.94 and 12.29 mgL-1 for dipping larvae after 48 and 72 h treatment. These results showed that, the 2nd larvae was more susceptible than 4th instars larvae to these compounds. In addition, the insecticidial activity of these compounds was more effective on cotton leaf worm larvae in feeding bioassay as compared with the dipping treatment. The rest of the tested compounds possessed moderate to strong larvicidal activities against cotton leaf worm. In general, the results indicate the possible use of 3,5-pyrazolidinedione derivatives as components in integrated pest management program against S. littoralis.