Potassium niobate (KNbO3) nanoneedles were synthesized on polycrystalline Al2O3 substrate by hydrothermal reaction. X-ray diffraction and Raman spectra analysis results indicated that the nanoneedles exhibit single-phase perovskite structure and are highly crystallized. High-resolution transmission electron microscopy showed KNbO3 nanoneedles grew along the [110] direction. Meanwhile, the second harmonic generation (SHG) response was investigated. The as-synthesized nanoneedles exhibited clearly SHG response, which means nanoneedles were efficient nanoscale second harmonic light source. The excellent nonlinear optical property of KNbO3 nanoneedles shows potential application in nano-optical devices. (C) 2011 Elsevier B.V. All rights reserved.