This study investigated the long-term durability of the interfacial bond in carbon fiber /polyetheretherketone (C/PEEK) and carbon fiber/polysulfone (C/PSF) composites after exposure to hygrothermal environments. A single fiber pull-out test was utilized to quantitatively determine the ultimate bond strength (UBS) of the samples following exposure. Samples were tested at three temperatures for six time periods and in two environments (dry and salt water). A mathematical model based on nth order chemical reaction kinetics was applied to describe the long-term durability of the interface. The results of this study indicate that interfacial bond strength in C/PSF and C/PEEK (380 grade) composites is significantly influenced by long-term exposure to salt water, especially at high temperatures. The results indicate that salt water saturation reduces interfacial bond strength in C/PSF and C/PEEK (380 grade) composites as a function of both time and temperature, with bond strength apparently reaching a stable temperature-dependent equilibrium level.