With the aim to explore the effect of heteroatoms on corrosion inhibiting efficacy of structurally similar azomethine based organic molecules, namely, 5-((furan-2-yl)methyleneamino)-2H-1,2,4-triazole-3-thiol (FMT) and 5-((thiophen-2-yl)methyleneamino)-2H-1,2,4-triazole-3-thiol (TMT) were synthesized and its corrosion inhibiting property were investigated by potentiodynamic polarization and non-destructive electrochemical impedance spectroscopy. These electrochemical techniques revealed the excellent corrosion inhibiting efficacy of synthesized inhibitor molecules for mild steel exposed to 1 molL⁻¹ HCl at ambient condition. Surface analyses using FESEM, AFM and contact angle measurement of mild steel retrieved from corrosive medium containing inhibitor molecules confirmed the formation of protective layer of inhibitor molecules on its surface. The consequences of efficient corrosion inhibiting property has been explained based on Hard-Soft-Acid-Base principle as well as electronegativity and polarizability difference of heteroatoms present in the skeleton of inhibitor molecules. Moreover, in order to validate the corrosion inhibiting property obtained from electrochemical experimentations, the insight of corrosion inhibition mechanism has been further explored by employing theoretical calculations viz density functional theory, Fukui indices analyses, molecular dynamics simulation and radial distribution function. Mulliken atomic charges, frontier molecular orbital and Fukui indices analysis of the free as well as adsorbed inhibitor molecules confirms the interaction of the susceptible reactive sites.