The corrosion inhibition of mild steel by 7-(ethylthiobenzimidazolyl) theophylline (7-ETBT) in 1 M HCl medium was investigated through weight loss and Tafel polarization techniques within a temperature range of 298 to 318 K. The inhibition efficiency depends on the concentration of 7-ETBT and reaction system temperature. The maximum inhibition efficiency values of 90.73 and 87.06 %, respectively, were estimated using both weight loss and Tafel polarization techniques at 298 K. The results suggest spontaneous and predominant physical adsorption of 7-ETBT on the metal surface which obeys Langmuir isotherm model. Furthermore, Tafel polarization method revealed that 7-ETBT is a mixed-type inhibitor. Potentiodynamic polarization results are in accordance with weight loss data to a good extent.