Interaction of organic molecules with the surface of metals plays important role in many applications. In particular, surface protective applications need much explanation from both experimental and theoretical point of view. Herein, we have investigated the surface adsorption characteristics and corrosion inhibition behavior of two new benzimidazole derivatives namely 2-(2-Bromophenyl)-1H-benzimidazole (BPBA) and 2-(2-Bromophenyl)-1-methyl-1H-benzimidazole (BPMA) on mild steel in 0.5MHCl solution using experimental and theoretical approach. Electrochemical and weight loss experiments were used to elucidate the corrosion inhibition potentials of BPBA and BPMA. Attenuated total reflectance-Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, and X-ray photoelectron spectroscopy measurements were performed to confirm the adsorption of BPBA and BPMA on mild steel surface. Computer simulations were further employed to provide additional insights into the mechanism of interaction between the inhibitors and the steel surface. All the results confirmed that BPMA is a better corrosion inhibitor for mild steel than BPBA in 0.5M HCl. This new inhibitors could find application industrially during processes such as oil well acidizing for steel protection against corrosion.