<p>Insect gut bacterial communities are significantly influenced by host plants. <i>Tuta absoluta</i> (<i>T. absoluta</i>), an invasive pest that damages tomato, eggplant, and potato plants of the <i>Solanaceae</i> family, causes significant economic losses. This study investigated the effect of different host plants on the composition and functionality of the gut bacterial community of <i>T. absoluta</i>. The gut bacterial community of <i>T. absoluta</i> fed on different host plants was investigated using high-throughput sequencing. Our results showed that the host plant significantly influenced the gut bacterial diversity. At the phylum level, Proteobacteria and Cyanobacteria consistently dominated the gut microbiota of <i>T. absoluta</i> larvae regardless of host plant species. Regarding genus-level composition, <i>Wolbachia</i> was the predominant genus in larvae fed tomato and potato, whereas <i>Enterobacter</i> prevailed in those reared on eggplant. Functional prediction analysis identified several enriched pathways, predominantly related to metabolism. These included enzyme families, biosynthesis of other secondary metabolites, metabolism of other amino acids, xenobiotics biodegradation and metabolism, carbohydrate metabolism, and glycan biosynthesis and metabolism. This study revealed significant variations in the community structures of gut microbiota in <i>T. absoluta</i> feeding on different host plants. These findings will improve our understanding of the gut microbiota of <i>T. absoluta</i> and its potential interactions with the host insect, thereby facilitating the development of microbial-based pest management strategies.</p>