Seismic response of liquefied natural gas tanks (LNG) is quite different from other structures not only due to hydrodynamic effects acting on the tank shell but also due to many sources of nonlinear behavior mechanisms of tanks. In this paper, the main seismic responses such as base force and overturning moment of conventional and isolated LNG tanks are investigated. Isolation system applied in this study is Friction Pendulum Bearing TM (FPB) that is installed between the tank and its foundation to protect it from damage due to earthquake shaking. Different parameters such as aspect ratio, coefficient of friction, and periodic time have been changed to study their effect on the seismic behavior of the LNG tank. FPB significantly reduces the main responses of the tank and so results reveal that the FPB seismic isolation system is very effective for using in LNG tanks.