This manuscript presents a study on a green corrosion inhibitor extracted from Elaeis guineensis (EG) leaves for mild steel (MS) exposed to acidic condition. Weight loss measurement was conducted at various temperatures to investigate the corrosion inhibitive behaviour of the aqueous extract in 1 M HCl solution. Results demonstrated that both inhibition efficiency (η%) and surface coverage (θ) had increased with increasing inhibitor concentration, but decreased with increasing temperature. After immersion for 72 h, the inhibition efficiency were between 60.48% at 319 K and 73.81% at 298 K. Adsorption of extract onto the MS surface was shown to obey Langmuir’s adsorption isotherm while the free energy value (