The lithium ion conducting solid lithium phosphorous nitride (LiPON) has been sputtered on the water-stable NASICON-type lithium ion conducting solid electrolyte Li1+x+y Al x Ti2−x P3−y Si y O12 (LATP). The stability and the interface resistance of the Li–Al/LiPON/LATP/LiPON/Li–Al cell have been examined. It is shown that the LiPON film protects LATP from reacting with the Li–Al alloy. The impedance of the Li–Al/LiPON/LATP/LiPON/Li–Al cell has been measured in the temperature range 25–80°C. The total cell resistance is about 8600Ωcm2 at room temperature and 360Ωcm2 at 80°C. The analysis of the impedance profiles suggests that the Li–Al/LiPON interface resistance is dominant at lower temperatures. The LATP plate immersed in water for 1 month shows only a slight degradation in the conductivity.