A novel functional carbon nanofiller CNTs-COOH-RD resistant to thermal-oxidative aging was prepared by grafting 1,2-dihydro-2,2,4-trimethyl-quinoline (antioxidant RD) onto the surface of carboxylated carbon nanotubes (CNTs-COOH) using γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560). Five groups of nitrile butadiene rubber (NBR) composites were prepared by mechanical blending, and the effects of CNTs-COOH-RD on the mechanical and tribological properties of NBR composites were investigated. The results showed that compared to pure NBR and free antioxidant RD-loaded samples, the tensile and tear strengths increased by approximately 23%, 5%, 18%, and 4%, respectively. The wear surfaces of the NBR composites were characterized using scanning electron microscopy and X-ray energy spectroscopy, which revealed the reinforcing mechanism of CNTs-COOH-RD. Molecular dynamics simulations were used to explain the thermal-oxidative aging mechanism of CNTs-COOH-RD from an atomic mechanism perspective. The results showed that the mobility of CNTs-COOH-RD within the NBR matrix was significantly reduced compared with that of the free antioxidant RD. The proposed functional carbon nanofiller enabled the NBR composites to exhibit superior mechanical and thermal-oxidative aging properties during the aging failure process.