Phycobiliproteins are essential accessory pigments that allow light capture and transfer of light energy from the sun to the reaction center so that photosynthesis can take place. They are mainly found in marine algae, such as cyanobacteria, red algae, and some cryptophytes. The most important are phycoerythrin, phycoerythrocyanin, phycocyanin, and allophycocyanin. They have unique antioxidant, antiinflammatory, and anticancer properties and unique absorbance and fluorescence properties, even as food additives such as coloring and antibacterial. Due to their fluorescent properties, they are used as a fluorescent label for various applications in immunoassays, such as flow cytometry fluorescence-activated cells, among others. In addition, it works as a nutraceutical because it is usually used to prevent kidney, liver, and brain damage, among many others. For this reason, they are of great interest in the biomedical, food, research, biotechnology, cosmetics, and nutraceutical industries, among others. This chapter will address the main phycobiliproteins, their nutraceutical and pharmacological properties, and their applications.