Blending polymers is used to obtain products with improved and wider range of properties. A polymer blend or polyblend is a microscopically mixture of two or more polymers. This paper deals with polyblend nanocomposites where one of the components has at least one dimension of the order of nanometer. It covers different groups of nanocomposites depending on the type of the polymer used in such mixtures, mainly:thermoplastic -thermoplastic polymer blend nanocomposites, thermoplastic -thermoset polymer blend nanocomposites, thermoplastic -elastomer polymer blend nanocomposites, biodegradable polymer blend nanocomposites.