A huge number of byproducts and wastes are derived from the processing of fishery resources, which, in the case of teleost fish, can represent up to 70% of the initial biomass. In industry, fishery wastes are destined to produce oil and fishmeal used to elaborate animal feeds. Nevertheless, biomass from fish wastes has an excellent potential to be an important source of bioproducts with high added- and commercial values, such as protein, peptides, gelatins, collagen, sulfated polysaccharides, and polyunsaturated fatty acids. Some of these biomolecules are used as food supplements due to their high nutritional value. Still, additionally, they can show one or several biological activities, the most notable being antioxidant, antihypertensive, anticarcinogenic, and antimicrobial, among others. Then, these bioactive molecules may further be used as food additives as well as to formulate nutraceutical and therapeutic products. Thus, aspects such as chemical composition, structural biochemistry of molecules with biological activities, and conventional and innovative biotechnological processes (e.g., enzyme and microbial processing) used to recover or produce such biomolecules from fish waste will be discussed in greater detail in this chapter.