Nanolayered polymer membranes, which have biomimicking layered structures, have been developed in recent years. The unique microstructures allow the membranes many potential applications. To facilitate the application of the membranes, the understandings of mechanical properties of the pristine and aged membranes are needed for the short and long-term applications. The current study focuses on the study of the relationship between the microstructure of the membrane and the mechanical properties including stiffness, strength, and ductility. The effect of the microstructure on the long-term application has been evaluated by thermal aging. The nanolayered polymer membranes have been subjected to thermal aging at various temperatures for different time frames. It has been found that the microstructure parameters, such as layer thickness, have great effect on the mechanical properties and thermal aging resistance. The thinner the layer of the membrane is, the better the strength and thermal aging resistance are.