The investigation of kinetics and thermodynamics of the corrosion of mild steel in a 2 M HCl solution using methanolic extract of Erigeron floribundus was carried out by means of gravimetric techniques. The results obtained indicate that the extract retarded corrosion. The inhibition efficiency was seen to increase with increase in concentration of the inhibitor, as well as with increase in temperature. The values of activation energy (Ea) obtained indicate a chemisorptions mechanism, whereas the value of Gibb free energy (ΔGoads) indicates a spontaneous adsorption of the extract components on the metal surface. Kinetic modelling of the experimental data obeys first order reaction. The adsorption of methanolic extract of Erigeron floribundus onto the mild steel surface followed the Langmuir adsorption isotherm model. Therefore, the extract functions as good corrosion inhibitor for mild steel in hydrochloric acid.