Preparation of the novel biodegradable composite based on carboxymethylated starch and cellulose matrix and plant fillers have been described. As a filler milled cereal husks of various origin: rye, spelt, and rice were used. Additionally, softwood flour was used for comparison. Introducing natural filler beneficially affected the mechanical parameters of the CMS/CMC system, as moisture absorption as well as solubility in water decreased (e.g. by ca. 7% and 6%, respectively for CMS/CMC with rice husk filler when compared to the neat system). Moreover the mechanical properties, i.e. Young's modulus and tensile strength increased. The chemical composition and size of natural fillers are essential factors determining the physicochemical properties of obtained composites, and cereal husks are promising raw materials for filling hydrophilic polysaccharide matrix.