Insects are promising alternatives to meet the world population’s demand for high-quality foods and to overcome important issues in animal farming practices. Novel and green biorefinery processes must be applied to insects, overcoming chemically based techniques. Eco-friendly approaches increase the nutritional value of insects, widening the commercial applications. This review addresses the rearing practices and nutritional composition of Tenebrio molitor, highlighting the green methodologies that can be applied to obtain value-added compounds, replacing unsustainable practices. Also, useful applications of pre-treated T. molitor biomass are presented with a thoughtful insight into their advantages and limitations. The nutritional richness of T. molitor is being successfully explored by resorting to physical and biological procedures, resulting in valuable compounds for food, feeding, and biomedical and biotechnological industries. Novel ingredients and additives of insect origin may upgrade food and feed formulation, while chitosan of T. molitor origin may upgrade the packaging industries of food and feed.