The corrosion inhibition of L80 carbon steel sheets in Khuff gas well environment with sulfisoxazole (SZ) as green inhibitor has been evaluated by mass loss, potentiodynamic polarization, electrochemical impedance spectroscopy and quantum mechanical studies. All these techniques reveal that the SZ inhibits the corrosion of L80 carbon steel in acidified H2S/CO2 environment. Polarization studies indicated that inhibitor is acted as mixed type. The adsorption of the compounds on L80 carbon steel surface follows Langmuir adsorption isotherm.