Wheat gluten composites with kaolin were prepared using compression molding, in the presence of glycerol as a plasticizer. The influences of kaolin content (0, 2.5, 5.0, 7.5, 10, 12.5 and 15.0 wt%) and probe sonication on the water resistance, degradation, mechanical, thermal and morphological properties of a wheat gluten-based bioplastic was investigate. The results showed that the mechanical properties of the wheat gluten-based bioplastic were significantly improved by the incorporation of kaolin. Scanning electron microscope (SEM) images revealed that, in comparison with a wheat gluten composite containing the same amount of non-sonicated kaolin, sonication effectively improved the dispersion of kaolin in the wheat gluten matrix, increasing tensile strength, thermal stability and water resistance. Also, sonicated kaolin could delay the degradation process of the wheat gluten-based bioplastic, indicating the potential agricultural application of these composites in the controlled release of the active contents of fertilizers. (C) 2019 Published by Elsevier B.V.