The significance of biologically active compounds extracted from food and agro-industrial waste lies in their potential to promote human health, reduce waste, support sustainable practices, create economic opportunities, and drive innovation in various industries. Compounds such as terpenoids, phenolic compounds, alkaloids, and flavonoids are known to possess various biological activities and efforts to harness these compounds contribute to a more circular and sustainable approach. Agro-industrial by-products are abundantly produced across the food production chain, and handling them requires nonbiological/biological approaches depending on the volume of waste and anticipated product. In view of this, the present book chapter provides an extensive information about the bioactive constituents extracted from agro-industrial waste and effective methods for their extraction and purification. The chapter also consolidates various applications of the bioactive compounds, particularly in the food and pharmaceutical industries.