Polysaccharides are versatile bio-based polymers with significant potential in different industries, due to their excellent biocompatibility, biodegradability, natural abundance, low cost, and capacity to regulate molecular transport. This research investigates the use of polysaccharide-based materials in two applications: controlled drug delivery and sustainable packaging. The first part focuses on pharmaceutical applications, where natural gums were investigated as hydrophilic matrix-forming excipients in tablets prepare by direct compression for controlled drug release. Particular emphasis was placed on understanding how matrix formation and drug–polymer interactions influence molecular diffusion and, consequently, drug-release behavior. The second part focuses on sustainable packaging applications, where pullulan-based films were investigated as functional barrier materials. The effects of formulation, particularly the incorporation of different plasticizers, were investigated in relation to the mechanical properties and barrier performance of the films. Water-vapor transmission rate (WVTR) and oxygen transmission rate (OTR) were evaluated to understand how formulation and polymer interactions influence molecular transport.