Although many different human activities such as the oil and gas sector, mineral production, utilities, transportation, etc. depend on the utilization of steel and its alloys, they are highly susceptible to corrosion, especially in acidic media. Hence, processing entails substantial material expenditures due to metal losses. In this regard, the inhibitory characteristics of the synthetic heterocyclic derivative (3aR,7S,7aS)-4,5,6,7,8,8-hexachloro-1,3- dioxo-1,3,3a,4,7,7a-hexahydro-2H-4,7-methanoisoindol-2-yl)benzenesulfonamide (MBSI) was studied against corrosion of C-steel in 0.5 M H2SO4 at 25-55 ◦C. The structure of the synthesized molecule was confirmed by FTIR, 1 H-NMR, 13C-NMR, and MS. Weight-loss, potentiodynamic polarization, electrochemical impedance spectroscopy, electrochemical frequency modulation measurements as well as theoretical analyses were employed in this investigation. The results showed that the investigated MBSI compound functions as an efficient inhibitor with a physical adsorption nature on the surface of carbon steel. MBSI concentration causes the inhibition efficiency to rise, reaching a maximum of 94% for the steel alloy corrosion at 37 × 10− 6 M and 25◦C. The synthesized compound was suggested to act as a mixed-type inhibitor. SEM surface analysis showed the construction of a protective layer at the carbon steel surface. DFT-based quantum chemical indices provided more insight into the inhibitory mechanism. Molecular dynamics (MD) simulations were also applied to predict the conformational adsorption change of the inhibitor on the iron surface. In addition, thermodynamic and kinetic parameters were calculated. The experimental results are largely consistent with the theoretical results.