Dietary calcium intake below the recommended levels is widespread worldwide. Therefore, there is an urgent need to identify and implement new sources of this nutrient. Fish bones are rich in calcium and bioactive peptides and can be used as ingredients for the manufacture of functional foods or to improve the technological properties of food. Thus, fish bones may be an interesting alternative to traditional sources of calcium, such as dairy products. This review analyzes the available information on processes related to the derivation of calcium from fish bones, including solubilization of hydroxyapatite, reduction of particle size to nanometer range, and addition of calcium-chelating peptides. These processes are highly relevant for obtaining ingredients with a high calcium content, high availability, and adequate sensory properties when added to foods. Thus, fish bone powder has immense potential as a source of bioavailable calcium for food fortification. In addition to the biological and technological considerations, the use of a usually discarded part of fish as a source of bioactive ingredients not only represents an advantage in terms of contributing to waste reduction in food processing but also provides an economic reward.