Insects and plants have been interacting for more than 350 million years, often resulting in species variability and radiation. Studying insect-plant chemical and mechanical interactions at different levels can help shed light on the complex factors driving the evolutionarily successful relationship between these two groups. This Special Issue focuses on the chemical and physical interactions between insects and plants to understand the functional significance of plant chemistry, plant surface structures, and their relationships with a broad range of ecological groups of insects, including pollinators, herbivores, and predators. The results of the investigations presented in this Special Issue can help develop effective management strategies to successfully control insect pest infestations or pollination strategies for diverse cropping environments.