Na0.5K0.5NbO3 ceramics and LiNbO3-substituted Na0.5K0.5NbO3 ceramics were prepared by the solid-state reaction method. The crystallization and grain morphology of the two types of ceramics were confirmed by X-ray diffraction and atomic force microscopy studies, respectively. The 5 mol% LiNbO3 substituted Na0.5K0.5NbO3 ceramics shows well-saturated ferroelectric P-E hysteresis loops. The dielectric and electrical properties of the ceramics were investigated in the frequency range from 10 Hz to 1 MHz and the temperature range from 25°C to 600°C. Analysis of the complex impedance relaxation by the Cole-Cole plot showed one impedance relaxation for LiNbO3 substituted Na0.5K0.5NbO3. The contributions of electrical conduction in the above mentioned temperature and frequency ranges are discussed.