Natural selection is notoriously dynamic in nature, and so, too, is sexual selection. The interactions between phytophagous insects and their host plants have provided valuable insights into the many ways in which eco- logical factors can influence sexual selection. In this review, we highlight recent discoveries and provide guidance for future work in this area. Impor- tantly, host plants can affect both the agents of sexual selection (e.g., mate choice and male–male competition) and the traits under selection (e.g., or- naments and weapons). Furthermore, in our rapidly changing world, insects now routinely encounter new potential host plants. The process of adapta- tion to a new host may be hindered or accelerated by sexual selection, and the unexplored evolutionary trajectories that emerge from these dynamics are relevant to pest management and insect conservation strategies. Examin- ing the effects of host plants on sexual selection has the potential to advance our fundamental understanding of sexual conflict, host range evolution, and speciation, with relevance across taxa.