In Egypt, the onion plants (Allium cepa L.) is considered as one of the most important field crops that are continuously and extensively grown and they are also spread and cultivated un a large scale all over the world. It can be grown under a wide range of climatic conditions, but they do best in a mild climate that is characterized by no excessive rainfall or extreme temperature. The onion crop is subjected to attack by a lot of important sap-sucking insects' pests such as; the onion thrips, Thrips tabaci (L.) (Thysanoptera: Thripidae), which cause obvious damage to the resulted crop. Obtained results indicated that in the area of the greenhouses that were cultivated with the onion plants for the unreleased control, the mean total numbers of the onion thrips, T. tabaci individuals per season were; 26.6±2.9 (18.8-41.2) and 27.9±3.4 (18.2-42.3) individuals, for 2018 and 2019 seasons, respectively. While, in the case of the released area of the adults of the ladybird beetle, Coccinella undecimpunctata L. (Coloeptera: Coccinellidae), the mean total number of the onion thrips, T. tabaci individuals for the two seasons together was 27.3(18.2-42.3) individuals., with a mean percentage of reduction for the two seasons together of 68.80% (69.90-68.40%). But, in the case of the released area of the larvae of the green lacewing, Chrysoperla carnea (Steph.) (Neuroptera: Chrysopidae), the mean total of the onion thrips, T. tabaci individuals for the two seasons together was 8.0 (2.5-19.5) individuals, with a mean percentage of reduction for the two seasons together of 70.6% (69.9-71.7%). Therefore, the obtained results revealed the important role of releasing the two predators; the ladybird beetle, C. undecimpunctata, and the green lacewing, C. carnea as effective biocontrol agents against the onion thrips, T. tabaci on the onion plants. So, they can be released in onion fields and/or other related fields that suffer from the pest attack, in the frame of Integrated Pest Management (I.P.M.) strategies, for decreasing the uses of the chemical control methods, to avoid the hazards of these direct or the indirect insecticidal applications on the pollution of the environment.