Unveiling the fundamental thermal-oxidative aging mechanism and thermal degradation kinetics of the poly(decamethyleneterephthalamide) (PA10T)/ glass fiber (GF) composites under different aging temperatures (160 degrees C, 200 degrees C, and 240 degrees C) for 0-50 days will facilitate the understanding of the interaction between matrix PA10T and GF. The results revealed that the decrease of mechanical properties referring to tensile strength, flexural strength and notched impact strength, and the occurrence of debonding phenomenon between PA10T matrix and GF were increasingly obvious after longer aging time at higher aging temperature. At the same time, the decline of crystalline was mainly ascribed to the thermal-oxidative aging effect, which triggered the deterioration of mechanical properties of PA10T/GF composites. Accordingly, the enhancement of rigidity were probably attributed to the higher temperature aging effect with the aging time prolonging in PA10T/GF composites, while the interfacial debonding between GF and resin matrix obviously occurred with the increase of aging time. In a word, it is believed that investigating the fundamental thermal-oxidative aging of PA10T/GF composites would be beneficial to optimize and control the service life and applications of materials. POLYM. ENG. SCI., 59:643-656, 2019. (c) 2018 Society of Plastics Engineers