In this study, composites from alkali lignin and wheat gluten, modified with different percentages of sodium silicate, were prepared and characterized. Moreover, the addition of silica to the aforementioned composites was studied with the aim of improving the thermal and mechanical properties. The effect of wheat gluten percent and the extent of its modification on the blends properties were investigated via diametric tensile strength, thermomechanical analysis (TMA), scanning electron microscope (SEM), thickness swelling and thermogravimetric analysis (TGA). The results showed significant improvement in the diametric tensile strength, thickness swelling, uniformity in the fracture surface, and the shift of glass transition temperature (T-g) toward higher values with increasing wheat gluten percent and its modification extent. These results reflect the enhancement of interaction between alkali lignin and wheat gluten Alkali lignin/wheat gluten blends filled with silica possessed distinguishable characteristics and improved diametric tensile strength, low thermal expansion, and high T-g. Interestingly, TMA results showed that high dimensional stability against heating (thermal expansion percent) Could be obtained using 60%, wheat gluten modified with 15% sodium silicate and filled with 10% silica. This sample showed the highest T-g and the lowest thickness swelling in addition to smooth, uniform, and glossy Surface as shown from the SEM images and TMA charts. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 793-801, 2009