Marine algae are sustainable and natural abundant resource that are rich in structural cell wall and storage polysaccharides. Marine polysaccharides are macromolecules with high diversity in monosaccharide composition, glycosidic linkages, structural configuration, molecular weight, and wide ranges of functional groups. Marine-originated polysaccharides have extensively employed in the development of advanced medical devices thanks to their biodegradability, biocompatibility, high mechanical strength, antitumor, anticoagulant, antiviral, antioxidant, and antimicrobial properties. These advantages combined with natural biodiversity of the marine polysaccharides are intriguing for the development of new generation of advanced biomaterials and medical devices. Furthermore, the use of natural biopolymers offers more sustainable, greener pathway for polymeric production and less dependent on the non-renewable fossil petroleum resource. Intriguingly, the properties of marine-based polysaccharide can be leveraged by the hybridization with different synthetic and natural materials, leading to the discovery of biocomposites with unprecedented performances. With a strong focus on sustainability, this chapter will discuss the therapeutic potential and biomedical applications of biocomposites derived from major natural marine polysaccharides from various brown and red algae focusing on alginate, agarose and sulfated galactan-carrageenan.