This paper presents an experimental and numerical investigation of the thermal behavior of thin phase change material (PCM) packages as a solution to thermal management in portable electronic devices. The thin packages are made of encapsulated PCM in aluminized laminated film. The experimental setup is designed to include the most fundamental aspects of a portable electronic system while also being simple enough to be easily simulated using the finite element method; it is rectangular in nature. Two different types of PCM are used for the experimental work; the commercially available PT-37 and n-eicosane. It was determined that the use of a thin PCM thermal energy storage package significantly improved the temperature behavior of the experimental setup, by reducing the rate of temperature increase at the heater and the back cover. The time needed to reach a critical cover temperature of 45°C was increased by 12 to 18% while the time for the heater temperature to reach 70°C was increased by up to 66%. Numerical simulations of the system were in good agreement with the experimental data.