Background:Sucking insect pests cause severe damage to cotton crop production. The development of insect resistant cotton cultivars is one of the most effective measures in curtailing the yield losses. Considering the role of morphological and biochemical host plant resistance (HPR) traits in plant defense, 12 cotton genotypes/varieties were evaluated for leaf area, leaf glanding, total soluble sugars, total soluble proteins, total phenolics, tannin and total flavonoids against fluctuating populations of whitefly, thrips and jassid under field conditions. Results:The population of these insects fluctuated during the growing season and remained above threshold level (whitefly>5, thrips>(8–10), or jassid>1 per leaf) during late June and early July. Strong and negative association of whitefly (r=?0.825) and jassid (r=?0.929) with seed cotton yield was observed. Mean population of insects were the highest in Glandless-1 followed by NIA-82 and NIA-M30. NIAB-Kiran followed by NIAB-878 and Sadori were the most resistant, with the mean population of 1.41, 1.60, 1.66 (whitefly);2.24, 2.32, 2.53 (thrips) and 0.37, 0.31, 0.36 (jassid), respectively. The resistant variety NIAB-Kiran showed less soluble sugars (8.54 mg·g?1), soluble proteins (27.11 mg·g?1) and more phenolic (36.56 mg·g?1) and flavonoids (13.10 mg·g?1) as compared with the susceptible check Glandless-1. Moreover, all insect populations were positively correlated with total soluble sugars and proteins. Whitefly populations exhibited negative response to leaf gossypol glands, total phenolics, tannins and flavonoids. The thrips and jassid populations had a significant and negative correlation with these four biochemical HPR traits. Conclusion:The identified resistant resources and HPR traits can be deployed against sucking insect pests\' complex in future breeding programs of developing insect resistant cotton varieties.