This study was conducted to investigate the performance of the Ti-6Al-4V/FM-5 adhesive bonded system for potential applications on high-speed aircraft. The long-term environmental aging effects on Ti-6Al-4V/FM-5 bonded joints and neat FM-5 and PETI-5 resin specimens were investigated. Dynamic mechanical analysis (DMA) and uniaxial tensile testing using dogbone samples were performed on neat FM-5 and PETI-5 resin specimens before and after high-temperature aging in both ambient and reduced pressure environments. Mode I fracture testing was also performed on beam specimens fabricated with mat-scrim-cloth-supported films of FM-5 adhesive bonding titanium adherends prior to and after environmental aging. Experimental results revealed that both physical aging, which is reversible, and irreversible chemical aging took place simultaneously in the adhesive systems, and both types of aging could contribute to loss in adhesive bond performance. Furthermore, the properties of several different Ti-6Al-4V/FM-5 systems, prepared using different surface pretreatment methods and different supportive matrices of FM-5 resin, were compared in this study, and the effect of mode-mixity on the fracture toughness of the adhesive-bonded systems was also evaluated by conducting double cantilever beam (DCB), end-notched flexure (ENF), and mixed-mode flexure (MMF) tests. The creep behavior of the Ti/FM-5 bonded joint was also investigated by performing thick adherend shear tests.