The corrosion inhibition of iron in 0.5 M sulfuric acid by N, N-dipropynoxy methyl amine trimethyl phosphonate has been investigated by means of the potentiodynamic polarization and electrochemical impedance spectrum (E.I.S) techniques. N,N-dipropynoxy methyl amine trimethyl phosphonate was studied in concentrations from 40 ppm to 320 ppm at a temperature of 298 K. The results show that the inhibition mechanism of N,N-dipropynoxy methyl amine trimethyl phosphonate is mixed controlled. It is also found that this inhibitor obeys the Frumkin adsorption isotherm and Flory-Huggins isotherm based on a substitutional adsorption process.