The rheological behavior of melt blends of ternary copoly(amides) synthesized by the copolycondensation of caprolactam, salts of adipic and sebacic acids, and hexamethylenediamine, as well as ε-caprolactam, ω-dodecalactam with the salt of adipic acid, and hexamethylenediamine, and potato starch was studied. The content of starch in the blends ranged from 5 to 20 wt %. Polymer systems were prepared using triacetin-water mixtures as plasticizing agents. The biodegradation ability of films prepared from the blends of copoly(amides) and starch was estimated. It was shown that the melts of the blends behave as strongly structured pseudoplastic systems: their flow begins under a yield shear stress of ≈103 Pa and appears to be non-Newtonian. An increase in the content of starch brings about a rise in the viscosity of both systems. This may be associated with the formation of strong intermolecular contacts between amide groups of copoly(amides) and hydroxyl groups of starch. It was found that the blends obtained combine the typical rheological properties of synthetic polymers and the ability to biodegradation.