Metals generally deteriorate with chemical attacks and reaction with environments. This paper investigates the effect of grape fruit extract on the corrosion of mild steel using weight loss and thermometric measurements. The concentration of the inhibitors used was varied from 0.1g/s to 0.5g/s in acidic medium. Standard concentrated HCl acid with density of 1.18g/cm3 and a percentage purity of 35% with a molar mass of 35.5g was used. The results shows that the corrosion rates obtained decreased with addition of different of concentrations of inhibitor with the lowest values were obtained at addition of highest concentration (0.5 g/l) of the studied extract. It could be observed that the temperature fluctuates with time and reach the peak at approximately 360 min and then decreased. The reason for this can be attributed to increase in blocking of free movement of corrosion product (Fe2+) by the adsorption of the inhibitor, thereby reducing the creation of more ions and its precipitates with increase in time. The weight loss of mild steel increased as the exposure time increases in the absence and presence of inhibitor. The higher the concentration of inhibition, the lower the corrosion rate and grape fruit juice is a good inhibitor of corrosion.