The present study aims at investigating the impacts of the extract of Trachyspermum leaves on the mild steel corrosion in 0.1M hydrochloric acid (HCl), while highlighting its inhibitory mechanisms. The effects of mild steel corrosion in solutions of HCl were examined using the gravimetric and galvanostatic polarization techniques, along with EIS analyses. According to the results, the maximum inhibitory effectiveness corresponding to the minimum corrosion rate could be observed at the highest desirable level of inhibitor concentration equal to 100 ppm, while the corrosion rate decreases with an increase in the extract concentration. The absorption examinations indicated the best description of the metal surface interaction by Langmuir isotherm, while obtaining the best exposure time for the Trachyspermum leaves extract adsorption into the surface of the metal in different concentration. Based on the results of polarization, the inhibitors can play the role of a mixed inhibitor, also confirmed by the computational data.