•Hydrogels made from polysaccharide polymers are widely used.•Their functional properties depend on their molecular structure and mobility.•Dynamic and responsive hydrogels are challenging for molecular characterization.•Modern solid-state NMR spectroscopy reveals structure and dynamics of hydrogels.•Information is obtained on the polysaccharides and also the associated water. Hydrogels find application in many areas of technology and research due to their ability to combine responsiveness and robustness. A detailed understanding of their molecular structure and dynamics (which ultimately underpin their functional properties) is needed for their design to be optimized and these hydrogels to be exploited effectively. In this review, we shed light on the unique capabilities of solid-state NMR spectroscopy to reveal this information in molecular detail. We review recent literature on the advancements in solid-state NMR techniques in resolving the structure, degree of grafting, molecular organization, water-biopolymer interactions and internal dynamical behavior of hydrogels. Among various solid-state NMR techniques, 13C cross polarization (CP) magic angle spinning (MAS) NMR is examined for its ability to probe the hydrogel and its trapped solvent. Although widely applicable to many types of polymeric and supramolecular hydrogels, the current review focuses on polysaccharide-based hydrogels.