The corrosion behaviour of 5,5'-(((2-hydroxypropane-1,3-diyl)-bis-(oxy))-bis-(methylene))-bis-(8-quinolinol) noted HBQ8 towards mild steel has been studied for corrosion inhibition of mild steel in 1 M hydrochloric acid (HCl) by weight loss, Tafel polarization and electrochemical impedance spectroscopy (EIS) techniques. Then the experimental results were confirmed by molecular dynamic simulation and DFT calculations. The results showed that the inhibition efficiency (% IE) of HBQ8 increased with increasing inhibitor concentration and decreased with increase in temperatures. It was found that HBQ8 behaved as a mixed type inhibitor. The adsorption process of inhibitor obeyed the Langmuir isotherm and the thermodynamic parameters were discussed. The results from the weight loss, electrochemical measurements and theoretical calculations are in good agreement.