This research deals with dynamics response of a Pol/BaTiO 3 nanowire including viscosity influences. The wire is also impressed by a longitudinal electric field. Hamilton's principle and Lagrangian strains are employed in conjunction with a refined higher-order beam theory in order to derive equations of motion. By combining nonlocality and small size effects of a unique model into the derived equations, the couple relations which describe nanosize behavior in a small scale are presented. By employing an analytical approach, the fundamental natural frequencies are calculated numerically. The important results display that the effect of internal viscosity and nonlocality whenever the nanowire is very large are pointless.