In the present work, 2-propyl-, and 2-heptyl-, 1H-benzo[d]imidazole were prepared by condensation reaction of o-phenylenediamine with n-butanoic acid and n-octanoic acid, respectively. The prepared products were characterized by FT-IR, 1H-NMR spectroscopy and melting point. These products were incorporated into acrylonitrile butadiene rubber (NBR) composites with two different fillers (Silica and High Abrasion Furnace carbon black HAF) as an antioxidant additive with different concentrations from 1up to 2 phr as a comparison with 2,2,4-trimethyl-1,2-dihydroquino-line (TMQ) as a traditional antioxidant. Their effects on the rheometric, physico-mechanical and electrical properties of NBR composites were evaluated. Thermo-oxidative aging was carried out for NBR composites and distribution of the prepared products observed by Scanning Electron Microscope (SEM).The results showed that the prepared products can act as highly efficient antioxidants in acrylonitrile butadiene rubber vulcanizates comparing with commercial antioxidant TMQ and revealed that there was enhancement in mechanical properties of NBR composites that containing the prepared products, as well. The results also illustrated that the optimum ratio from 2-alkylbenzimidazole incorporated into acrylonitrile butadiene rubber vulcanizates is 1.5 phr if compared with the same ratio from traditional antioxidant (TMQ).