The inhibitive action of Theobromine on corrosion of mild steel in 1M HCl solution has been studied using weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. It was found that the inhibition efficiency of Theobromine inhibitor increases with increase in concentration of inhibitor and decreases with increase in temperature. The inhibitor show corrosion inhibition efficiency of 90% at 1g/l and 308 K. Polarization data suggested that the Theobromine inhibitor used as mixed type inhibitor. Impedance measurements indicating that the corrosion reaction is controlled by charge transfer process. The adsorption of Theobromine on the metal surface was found to obey Langmuir adsorption isotherm. The Density Functional Theory (DFT) was employed for quantum chemical calculations to correlate the experimental findings.