Marine-derived polysaccharides have garnered significant interest due to their functional attributes and diverse applications in the culinary, pharmaceutical, food, and biomedical industries. This chapter provides an in-depth review of the structural, physicochemical and the use of most popular marine polysaccharides, including alginate, fucoidan, chitosan, carrageenan, and agar, as natural carriers for the entrapment and delivery of nutraceuticals and bioactive compounds. These biopolymers are valued for their structural versatility, biocompatibility, and ability to form stable matrices, making them ideal candidates for various purposes. Encapsulation plays a vital role in protecting environmentally sensitive bioactive ingredients from volatile losses, oxidative degradation, decomposition under harsh processing conditions, handling, and storage, and interaction with other molecular entities in the surrounding medium, while preserving the color, flavor, texture, and aroma of the matrix in which they are embedded. Additionally, encapsulation can mask the undesirable flavor and odor of the nutraceuticals and facilitate their safe delivery to the targeted sites when ingested orally. Many marine polysaccharides, owing to their gel-forming and emulsifying properties, serve as effective wall materials for encapsulation applications. A wide range of techniques is employed for the encapsulation of bioactive ingredients, with spray drying, freeze-drying, and coacervation being the most commonly utilized methods in the food and pharmaceutical sectors. However, future research is required to focus on the modification of marine polysaccharides and their based-delivery systems, including enzymatic hydrolysis, chemical derivatization, and nanotechnology-based methods, to improve their functional properties and enhance the effectiveness of the corresponding designed delivery matrices.