Herbivorous arthropods represent a major threat to crop production worldwide, and their management still relies heavily on chemical pesticides. However, resistance development and increasing concerns about environmental and human health impacts have stimulated interest in alternative, ecologically based control strategies. Exploiting plant-mediated defenses and multitrophic interactions is a promising approach in the context of Integrated Pest Management (IPM). In parallel, the rapid expansion of insect farming has generated large quantities of residual by-products, creating new opportunities for their valorization in agriculture. Insect frass, a nutrient-rich by-product of insect farming, is increasingly used as a soil amendment in agriculture and has been reported to stimulate plant defense responses against herbivorous pests. In this study, we investigated the plant-mediated effects of insect frass on herbivore performance in tomato plants. Plants were treated with frass derived from two insect species, Tenebrio molitor and Hermetia illucens, and subsequently infested with two economically important arthropod pests, the two-spotted spider mite (Tetranychus urticae) and the tomato russet mite (Aculops lycopersici). Herbivore performance was evaluated by recording survival, oviposition, and population growth of the pests. Comparisons were made between frass- treated and untreated plants to determine the potential of insect frass to induce plant defence against key arthropod pests. Our findings highlight the potential role of insect frass as a sustainable pest control tool in IPM, supporting circular economy principles while contributing to reduced reliance on chemical inputs The research project “Insect Frass for Sustainable Pest Management (INSECTFRASS)’ is implemented in the framework of H.F.R.I call “3rd Call for H.F.R.I.’s Research Projects to Support Faculty Members & Researchers” (H.F.R.I. Project Number: 23673).