: This paper presents a dynamic energy management policy for a wireless video streaming system, consisting of a battery-powered client and a video server. The video quality in wireless streaming is a function of three factors: the encoding aptitude of the server, the decoding aptitude of the client, and the wireless channel conditions. First, the energy consumption of a wireless video streaming system is modeled considering these factors, and then, a model of the wireless video streaming system is presented. Using the proposed model, the optimal energy assignment for each video frame is derived so as to maximize the system lifetime while satisfying a given minimum video quality requirement. Experimental results show that the proposed policy increases the system lifetime of a wireless video streaming system by an average of 20%.