Blends of poly(N-vinyl-2-pyrrolidone) (PVP) and sodium alginate (NaAlg) were prepared by casting from aqueous solutions. These blends were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and tensile strength test. The miscibility in the blends of PVP and NaAlg was established on the basis of the thermal analysis results. DSC showed that the blends possessed single, composition-dependent glass transition temperatures (T(g)s), indicating that the blends are miscible in amorphous state. FT-IR studies indicate that there are the intermolecular hydrogen bonding interactions, i.e., -OH center dot center dot center dot center dot center dot O = C in PVP/NaAlg blends. This blend films also exhibited the higher thermal stability and improved the elongation at break in dry states.