Evaluation the efficiency of Chrysoperla carnea (Stephen) second instar larvae was used in an experiment at the Qaha Agricultural Research Station in Qalyubia governorate in reducing the population of cotton leafworm Spodoptera littorals (Boised.) on cotton plants. During the 2021 and 2022 cotton seasons artificial infestation with the cotton leafworm S. littoralis was carried out inside tightly closed cages, where ten plants were randomly selected from each replicate. The infestation rate was determined by examining and determining the average number of S. littoralis larvae inside the cage to calculate the numbers required to release C. carnea for the different release levels. The C. carnea second instar larvae were released on the plants, at three rates (two, three, and four larva per meter square of cage) and a total of 3 releases were made at 14 days interval. In the first season 2021, the release of C. carnea showed the highest biological control activity fourteen days after the third release, resulting in a significant reduction in the numbers of S. littorals larvae. Our results demonstrated that the release of 2nd instar larvae of C. carnea at the three different rates of 2, 3, and 4 larvae/m2 induced a general reduction in S. littoralis larvae populations compared to the control treatment. The statistical analysis revealed that the efficiency of 2nd instar larvae of C. carnea was more evident when released at 4 larvae/m2 as a biocontrol agent against S. littoralis larvae attacking cotton plants under cadge.