We have used weight loss measurements, potentiodynamic polarization, and lectrochemical impedance spectroscopy to study the inhibiting effect of N,N–di(polyoxyethylene)–4–dodecylaniline, with different numbers of oxyethylene units, on corrosion of steel in a 1 M hydrochloric acid solution. We have determined that the studied compounds are good corrosion inhibitors. The inhibition efficiency increases with an increase in inhibitor concentration, an increase in the number of oxyethylene units in the chain of the inhibitor, and a decrease in temperature. The inhibiting effect of the studied compounds is due to blocking of the metal surface as a result of adsorption of the oxyethylene units of the inhibitor. The adsorption process is described by the Freundlich isotherm. The indicated compounds act as mixed (mostly anodic) corrosion inhibitors. We calculate some thermodynamic corrosion parameters.