The challenges of world population rise include providing food, reducing the depletion of natural resources, developing the agricultural food industry, preserving biodiversity, and using alternative sources. Since lignocellulosic agro-waste is the most prevalent organic compound in the world, it has enormous potential for sustainable application. Because of its abundance, renewability, and biodegradability, it is an important and sought-after source for the creation of materials in many different industries. Barley (Hordeum vulgare L.) may be grown in many different climates and geographical locations, and it is currently farmed in all temperate climatic regions. Barley has the potential to be the perfect crop for making nutritious food, feed, and straw fiber. Barley straw falls into this group and is a valuable crop because of its availability and abundance. Barley straws can be used as a renewable supply of lignocellulosic fibers, which is a more sustainable way to reduce excessive levels of agro-residue. There is a high cellulose, lignin, and hemicellulose content in this waste. Barley cellulose fibers possess enormous potential as a useful raw material for a range of applications, including substitutes for wood fibers, the manufacture of textiles, paper industries (pulp, paper, wipes, fiber-based packages), bioplastics, and thermal-electric power, clay-fiber composites in construction, growth medium, insulation material, enzymatically decomposed intermediate products for targeted applications. Notably, there is a dearth of genetic research on barley fiber. The application of biotechnology, like transgenics and molecular technologies, to various activities can benefit conventional barley fiber breeding. Therefore, this chapter delves into the world of barley fibers through its importance and uses, barley straws, barley fibers and industry, current cultivation practices and challenges, germplasm biodiversity and conservation, conventional breeding, molecular breeding, and biotechnology methods.