The effect of 5-chloro-1-(2-(dimethylamino) ethyl) indoline-2,3-dione as a corrosion inhibitor on mild steel in 1M HCl solution was studied through weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was employed to analyze the surface topography of the uninhibited and inhibited mild steel. The inhibition efficiency of the inhibiting compound increases with increase in inhibitor concentration at 303K, resulting in significant decrease in corrosion rate of the mild steel. Thermodynamic adsorption and activation parameters were calculated for the corrosion inhibition process adsorption of 5-chloro-1-(2-(dimethylamino) ethyl)indoline-2,3-dione on the steel obeyed the Langmuir adsorption model.