Water-soluble fullerene-bearing pullulans were successfully prepared by the addition reaction of azide-substituted pullulans with fullerene C-60. The chemical structure of the products was characterized by IR, UV, and NMR spectroscopy. It was found that the saturation solubility of the C-60 moiety strongly depends on the degree of substitution (DS) of the sample, indicating that an optimum DS value of the C-60 moiety exists for its aqueous solubility.