Abstract: This study focused on the development of polysaccharide-based hydrogels with antioxidant and antibacterial properties. Using sodium alginate (SA), tannic acid (TA), and silver nitrate as raw materials, this study leveraged the reducing power of the hydroxyl and carboxyl functional groups inherently present in SA and TA to reduce the silver ions. The developed process provided sodium alginate-silver (SG) and sodium alginate-tannic acid-silver (STG) hydrogels. A comprehensive suite of analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG), was employed to elucidate the structural, morphological, and thermal stability characteristics of the synthesized hydrogels. Furthermore, the antioxidant and antibacterial activities of the hydrogels were also assessed comprehensively. The findings revealed that SA and TA could form a complex stabilized by hydrogen-bonding interactions, and both the carboxyl and hydroxyl groups in the complex participated in the reduction of silver ions. The uniform dispersion of silver particles within the gel matrix, along with the enhanced crosslinking of the polysaccharide chains of SA by TA and silver particles, significantly decreased the adsorbed and bound water content in the hydrogel. This, in turn, influenceed the structural integrity and thermal stability of STG hydrogels. The results of free radical scavenging and bacteriostatic experiments showed that the free radical scavenging rate and inhibition rate of STG hydrogel against E. coli could reach more than 90%, showing good antioxidant and bacteriostatic activity. Notably, the hydrogel preparation method is simple and ecofriendly. This study provides valuable theoretical and experimental insights into the development and application of multifunctional polysaccharide-based hydrogels with antibacterial properties.