Theoretical studies have been carried out using DFT, ab initio MP2 and Monte Carlo (MC) simulations of corrosion inhibitors from lawsone derivatives against carbon steel. The research focuses on studying the effect of substituent groups in the lawsone structure on the efficiency of corrosion inhibition in mild steel. Quantum chemical parameters of lawstone inhibitors in neutral and protonated conditions have been calculated. Fukui’s function analysis predicts that the active side of the inhibitor will be adsorbed on the mild steel surface. MC simulation is used to understand the adsorption patterns of lawsone compounds on metal surfaces. The organic inhibitor L-NH2 has better performance as a corrosion inhibitor for mild steel in neutral or protonated conditions.