Benzyl isothiocyanate (BITC) was used as anticorrosive agent for the corrosion mitigation of stainless steel in 0.5 M hydrochloric acid medium. The corrosion inhibition study of (BITC) was investigated by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques in the temperature range of 303–323 K. The study was done to get optimum inhibition efficiency. The surface morphology was studied using scanning electron microscopy (SEM). Elemental mapping was done by energy dispersive X-ray (EDX) studies. Suitable mechanism was proposed for corrosion and inhibition process. Quantum chemical calculations were done and discussed in detail using density functional theory (DFT). Maximum inhibition efficiency of 86% was achieved for the addition of 0.025 g L−1 of the inhibitor at 308 K. BITC acted as mixed inhibitor and obeyed Langmuir adsorption. Surface morphology studies reaffirmed the adsorption of BITC onto the surface of steel. Quantum chemical calculations supported experimental observations.