The present study highlights the inhibition performance of celery seeds (CS) extract on carbon steel immersed in 1M HCl, using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. This extract is selected due to biodegradable, renewable, and foremost aspect, is safe towards both the human being and environment. The studied inhibitor was easily extracted by using a simple aqueous extraction procedure. The experimental results show that the investigated inhibitor can effectively retard the corrosion process that occurs to carbon steel in hydrochloric acid solution. Electrochemical impedance spectroscopy (EIS) spectra showed that inhibition efficiency increases with the increasing of (CS) extract concentration. Among the studied inhibitor showed maximum inhibition efficiency of 96,86% at 250 ppm. Polarization curves indicate that (CS) extract acted as mixed type of inhibitors with a predominant effect on the anodic reactions. Basic calculations for the adsorption studies were also carried out. The adsorption of the extract onto carbon steel surface followed the Langmuir adsorption isotherm.