The two field experimentswere carried out at the Experimental Farm, Faculty of Agriculture, Saba Basha, Alexandria University, Alexandria Governorate, Egypt, during the two winter seasons of 2018/2019 and 2019/2020 to study the effect of foilar application of silicon forms on yield, quality and trips population of some onion varieties. This experiment was laid out in split-plot design in three replications in both seasons. The main plot was four onion varieties named; Giza Red, Giza 20, Hybrid Red (Al-Hamra), and Hybrid Yellow (Alabkar), while the subplots were differentsilicon forms (water = control, nano silicon, silicon in tablets, and silicon in powder form) was in both seasons. The obtained results showed that onion varieties differed in the studied characters, foliar application of the different forms of silicon significantly affected yield, and trips population, as well as the interaction between varieties and Si form, was significant in both seasons. Whereas on the other hand, Giza Red recorded the highest values of the studied parameters followed by Giza 20 as compared with the other varieties, also silicon in form nanoparticles (Si NPs)increased growth, yield quality, and decreased population of thrips in onion in both seasons. The interaction between Si forms and onion varieties was significant on all the studied characters, where planting Giza 20 with foliar application of nanoparticles (Si NPs) form recorded the highest values also reduced the population of thrips in the two cropping seasons under the study conditions.