Both leaf morphology and chemistry play a potential role in predicating with the population density of organisms. The current study was conducted, at the experimental farm of Mansoura University, to examine the effect of host plant species and their morphological (trichome density, thickness, and length) and physiological ((i.e., total protein, total carbohydrates, NPK) characteristics on population density of some piercing-sucking insect pests during two successive growing seasons.The number of Aphis spp. was positively correlated with the higher ratios of total protein, total carbohydrates, and N of squash leaves. While the numbers of Bemisia spp. and N. viridula, were positively correlated with the higher ratios of P and K of eggplant leaves. In contrast, Empoasca spp. exhibited higher populations on common bean leaves that were poor in all chemical compounds. Host plant species significantly affected the population density of all insects investigated. Squash harbored the higher numbers of Aphis spp., eggplant harbored the higher numbers of Bemisia spp.and N. viridula, and common bean had the higher number of Empoasca spp. The populations of aphids, whiteflies, green bugs, and leaf hoppers varied among leaf morphological types. Whitefly and green bugs exhibited significantly higher density on eggplant with more hairiness and hair length, whereas aphids had significantly higher populations on squash leaves with higher hair thickness. Common beans, with lower magnitude of density, thickness and length had the higher populations of leafhoppers. Based on leaf features and their chemical composition, common bean seems to be more resistant against infestation with aphids and whiteflies, squash against green bugs, and eggplant against leafhoppers.