Corrosion inhibition of C-steel in HCl solution using CdS and CdS/Polymethylmethacrylate hybrid has studied by weight loss, Tafel polarization and electrochemical impedance spectroscopy. The results show that CdS acted as a good inhibitor and this inhibition efficiency enhanced by using CdS/ PMMA hybrid. This inhibitory action increases with increasing the inhibitor concentration but decreases with rising the temperature. Polarization curves indicated that both CdS and CdS/PMMA acted as mixed inhibitor. Thermodynamic study revealed that the adsorption of CdS and CdS/PMMA obeys the Langmuir isotherm. The inhibition effect of the investigated inhibitors confirmed by EDX and XRD techniques.