The demand for sustainable protein sources for companion animal nutrition has stimulated interest in insect-derived ingredients. Tenebrio molitor larvae meal is a promising alternative to conventional proteins because of its nutritional composition and functional properties. This study evaluated the nutritional quality, in vitro digestibility, chitin digestibility, and antioxidant properties of T. molitor meal using canine- and feline-adapted in vitro digestion models. Chemical composition, amino acid and fatty acid profiles, total, protein, lipid, and chitin digestibility, antioxidant activity (ABTS), and Folin–Ciocalteu reducing capacity were determined. T. molitor meal contained 44.3% crude protein and 21.0% ether extract, with a balanced amino acid profile and a lipid fraction dominated by oleic and linoleic acids. Compared with the fish meal evaluated in this study, T. molitor showed higher total and lipid digestibility in both models, whereas protein digestibility was higher in dogs and comparable in cats. Chitin accounted for approximately 7.6% of the meal and showed negligible apparent digestibility. Water extracts of T. molitor exhibited greater antioxidant activity and reducing capacity than fish meal. These findings support the potential of T. molitor larvae meal as an alternative protein ingredient for companion animal nutrition, although in vivo studies are needed to confirm these observations.