This chapter focuses on the importance of bio-mordants, exploring their significance in reshaping the landscape of sustainable textile coloration. Bio-mordants, nature’s alternative to traditional chemical mordants, are introduced and defined, unraveling their unique role as catalysts in fabric dyeing processes. The chapter highlights various sources of bio-mordants, elucidating their diverse properties and introducing them into the intricate chemical structures that distinguish them. A detailed exploration of the extraction processes employed to harness these bio-mordants from natural sources adds depth to the understanding of their sustainable origins. The application of bio-mordants in textile coloration takes center stage, as the chapter navigates through their use on different fabrics, encompassing both natural and synthetic fibers. The performance of bio-mordants in the context of natural dyeing is thoroughly investigated, showcasing their efficacy in achieving vibrant and eco-friendly colors. A crucial aspect explored in this chapter is the underlying mechanism behind the interaction between bio-mordants and fabric coloration. This intricate relation between natural catalysts and textile fibers is unraveled, shedding light on the dyeing processes that define the success of bio-mordants in achieving sustainable and aesthetically pleasing outcomes. Therefore, this chapter not only defines and explores the properties of bio-mordants but also provides a comprehensive understanding of their extraction methods, application across diverse fabrics, and the intricate mechanisms that underpin their role in the evolution of sustainable textile coloration.