Silicone acrylic-urethane/amino-silane coatings are considered as promising candidates for use as a topcoat in high-temperature engineering applications. However, under these conditions, their functional properties can be affected, and it is well known that the loss of functional properties is related to modification of the chemical structure. The main objective of this first study is to identify the main criteria for degradation and establish a mechanism of degradation. For this purpose, the thermo-oxidative ageing of the topcoat is studied at the molecular scale using FTIR coupled with chemical treatments, TGA, and SPME/GC-MS. These complementary techniques allow the study of both the solid and gas phases and provide evidence for a more comprehensive degradation mechanism of this topcoat. The results show that degradation occurs on the labile hydrogen atoms located on the tertiary carbon of the acrylate group and on the α-position of the ester and amide. The solid phase oxidation products were identified as anhydrides and amides, whereas volatile products such as lactones and siloxanes were identified in the gas phase.