The aim of the present work is to investigate the inhibitory effect of the aerial part of Daucus carota L essential oil (EO) on mild steel in a 1.0M HCl solution. The electrochemical study is performed using potentiodynamic polarization (PDP) curves, and electrochemical impedance spectroscopy (EIS) measurements in the presence of various concentrations of the examined Daucus carota L essential oil (EO). PDP results show that the studied EO behaved as a mixed-type inhibitor. EIS measurements indicated that the EO could inhibit the corrosion of mild steel by the formation of a protective film on the surface of mild steel. The experimental results showed an efficiency of 96.5% for a concentration of 2 g/l. In addition, The DFT results proved that the major components, especially -pinene (23.5%), -Bisabolene (3.96%), and Pseudo limonene (7.20%) having a high electron-accepting ability and interact actively with the iron surface, which may be responsible for the inhibition ability of the investigated EO. Furthermore, the computational complies with the experimental data.