Tensile and fatigue tests were conducted at 50 and 70 degrees C for evaluating the mechanical behavior of polyethylene-terephthalate (PET) supported silver (Ag) thin films. The strain amplitude-number of cycles (S-N) curves of Ag/PET at elevated temperatures were acquired for determining the failure life under in situ heating condition. The stretchability at elevated temperature was found to be better than the tensile behavior at room temperature, whereas the fatigue behavior is worse at elevated temperature. The adhesion between silver and PET is better at elevated temperature. However, the tensile and fatigue characteristics were different results because the adhesion of silver and PET is not homogeneous at elevated temperatures. The good adhesion between thin metal films and flexible substrates is not always beneficial effect of the mechanical behavior. Therefore, we suggest a new fatigue failure mechanism for Ag/PET at elevated temperature. (C) 2017 Elsevier B.V. All rights reserved.