To prepare a novel series of silver (I) complexes, the interaction of benzimidazolium salts having their two nitrogen atoms substituted by bulky groups with Ag2O in DMF has been carried out. Their structures were characterized by elemental analyses, H-1 NMR, C-13 NMR and IR spectroscopy techniques. Further, the antibacterial properties of both the salts and their silver(I)-NHC complexes were tested against positive and negative bacteria using the agar dilution procedure. The results show that silver complexes are effective against Salmonella Typhimurium, Listeria monocytogenes, and Micrococcus luteus with moderate to high activity, and their minimum inhibitory concentrations ranging from 0.0024 to 1.25 mg/ml. Moreover, the antioxidant activity determination of these compounds were studied with the DPPH, and compared with (gallic acid "GA"and butylatedhydroxytoluene "BHT "). They exhibited significant antioxidant activities. In addition, the of benzimidazoles salts 2a-j and silver-NHC complexes 3a-j were screened for their antitumor activity. The highest antitumor activity was observed for 3e and 3d Complexes and they exhibited IC50 values 6.85 mu g/mL against MCF-7 and 10.75 mu g/mL against T47D, respectively. (C) 2019 The Authors. Published by Elsevier B.V. on behalf of King Saud University.