The properties of two poly(N-vinylpyrrolidone) derivatives containing ∼40 wt % star-shaped macromolecules with fullerene C₆₀ as a branching core were studied by the methods of electrooptical Kerr effect, dielectric polarization of macromolecules in solutions, and viscometry. It was shown that a polar nanoparticle (fullerene amino adduct) that appears after covalent addition of end groups of poly(N-vinylpyrrolidone) to C₆₀ drastically changes the electrooptical and dielectric characteristics of the parent polymer. It was demonstrated that the fullerene core appreciably affects the size and molecular density of star-shaped poly(N-vinylpyrrolidone) samples in solution.