The interactions between plants and insect herbivores play crucial roles in ecosystem functions and services. Ongoing climate change can affect these interactions through different mechanisms either directly or indirectly. In this review, we outline key ecological traits through which organisms respond to climate change. These include morphology, physiology, and chemistry for plants, and morphology, physiology, and behaviour for insects. We highlight how the responses of those traits to a changing climate might consequently affect herbivory. We propose key ecological questions that need to be addressed for each perspective of plant and insect traits, and we suggest novel approaches for answering these questions. Looking forwards, we outline fruitful areas for exploration of the ecological mechanisms underlying how plant–insect herbivore interactions might respond to climate changes from trait-based approaches.