Allium sativum (garlic) is well known for its medicinal and culinary properties, and it has a long history of practice spanning centuries. Beyond its bulb, garlic yields valuable by-products that are potent sources of bioactive phytochemicals. This chapter examines the wide range of bioactive compounds in garlic by-products and considers their potential in various domains, including pharmaceuticals, agriculture, and nutraceuticals. Key topics discussed include the components of garlic and garlic by-products, such as stems and leaves, peels, and bulbs, as well as their bioactive components, including allicin, flavonoids, saponins, and organosulfur compounds. This chapter also covers the extraction processes, highlighting conventional and modern techniques. In addition, the therapeutic potential of both garlic and garlic by-products is illuminated, including their antioxidant, cardiovascular, antidiabetic, and antimicrobial effects. Furthermore, the study delves into the possible applications of each garlic product’s nutraceuticals, non-food, and food applications. The chapter concludes with an emphasis on the necessity for more research into the bioavailability, commercial viability, and safety of garlic by-products as valuable sources of bioactive phytochemicals.