Polyether ether ketone (PEEK) composites face concurrent ultraviolet (UV) and thermo-oxidative aging in real-world service environments, yet the synergistic effects remain poorly understood. This study systematically decouples the degradation pathways of three PEEK-based materials--neat PEEK (PK), 30 wt% CF-reinforced PEEK (UG), and PTFE/Gr/CF-modified PEEK (VMT)--under isochronal (1500 h) UV and thermo-oxidative aging, establishing a comprehensive structure-property evolution chain. UV aging causes more severe surface oxidation and performance deterioration than thermo-oxidative aging across all materials. Carbon fibers effectively mitigate UV-induced degradation, enabling UG to achieve the highest compressive strength retention (81.0% after UV).