Thrips tabaci Lind. commonly called as onion thrips, is important foliage feeding pest of vegetables crops of Pakistan. For this research Ten onion accessions Early red, Phulkara, Chiltan, Saryab red, Swat-1, Hazara, Nasarpuri, Red imposta, VRIO-7, VRIO-8 were evaluated during rabi season of 2017-18 at Chak Shahzad, Islamabad (33o 40 N and 73o 08 E), for their susceptibility to onion thripsunder field conditions. Seeds of different onion varieties were obtained from Ayub Agriculture Research Institute Faisalabad (AARI), National Agriculture Research Center Islamabad (NARC) and BARC Quetta. Experiments were planned as Randomized Complete Block Design (RCBD) which were replicated five times. The plot size was kept at 3.0 × 3.0 m, with ridge to ridge distance of 15 cm and 10 cm onion plant-to-plant distance on each ridge. Fertilization, irrigation, weeding and all other agronomic practices were carried out in onion experimental fields except thrips management practices. Results revealed that thrips incidence occur after 6th week of transplantation. Saryab red found relatively susceptible against thrips with maximum mean population of 52.41±15.42 individuals per plant while Red imposta was relatively resistant with 37.02±9.97 individuals per plant infestation. Thrips tabaci showed maximum activity at 24 oc which shows positive correlation between temperature and thrips development. Considering categorization of ten onion accessions against thrips, Red Imposta was found as highly resistrant, early red, Chiltan, Nasar puri as resistant cultivar whereas Swat 1, Virio7 and 8, Phulkara, Saryab red were found susceptible while Hazara grouped in highly susceptible category due to maximum thrips infestation. Visual assessments depicted that all resistant cultivars had yellowish-green leaf color whereas the cultivars with blue-green foliage showed susceptibility towards thrips infestation. The Red imposta had lowest thrips infestation suggesting strong antibiosis and antixenosis.