Nanocomposite dispersions from polyester-type polyurethane and mixtures of the polyurethane with various biopolymers such as hydrolysed collagen, k-elastin, chondroitin sulphate or hyaluronic acid containing different concentrations of in situ generated silver nanoparticles (Ag NPs) were prepared and studied for application as antimicrobial materials or coatings. The influence of Ag NPs presence and of the dispersion composition on the rheological properties, microstructure of polyurethane/biopolymers-based dispersions and on the morphology of the solvent cast membranes obtained was investigated. The rheological measurements performed emphasizing on crossover point changes and relaxation time spectra investigation showed an increased restriction of chain movements in polyurethane as a consequence of increasing Ag NPs content and the complex viscoelastic response determined by chain rearrangements within macromolecules under flow disturbances with significantly modified relaxation times due to the presence of biopolymers. The Ag NPs distribution within polymeric dispersions was studied by TEM. It was found an ordered distribution of the spherical Ag NPs within PU-based matrix and formation of aggregates in both PU-biopolymers dispersions containing either chondroitin sulphate or hyaluronic acid, well-correlated with the rheology results. The morphology study by scanning electron microscopy evidenced the influence of Ag NPs dispersion degree and of natural compounds in composition on the aspect of the casted nanocomposite membranes.