Potassium sodium niobate nanopowders (KNN-NPs) were successfully synthesized by a modified sol-gel method, using starch as the stabilization and polymerization agent. Thermogravometric analysis (TGA) and differential thermal analysis (DTA) techniques were used to determine the needed temperature for the calcination of the prepared gels which is obtained to be 600 degrees C. Structural and optical properties of the prepared samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis spectroscopy. The XRD patterns of the synthesized samples confirmed that the structure of the prepared powders, calcined at 600 degrees C, are orthorhombic. TEM images showed that the particles of KN, NN, and KNN compounds have cubic shape with the average size of 26, 58, and 34 nm, respectively. Type of the optical band gap of the samples was found to be indirect, using UV-Vis diffused reflectance spectroscopy along with Kubelka-Munk method. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B. V. and The Society of Powder Technology Japan. All rights reserved.