The current study aims to explore the anti-corrosion performance of Poly [2-amino-4(1-benzyl-1H-indol-3-yl) thiophene -3- carbonitrile)] (PABITC) on C-steel in in 0.50 M H2SO4 using weight loss and potentiodynamic polarization measurements (PDP).. PABITC was synthesized with different molecular weights 882, 921, 1388, 15788 g/mol using APS as an oxidizing agent. The chemical structure of the polymer was characterized using H1NMR, DNMR, C13NMR, and FTIR spectroscopy . Polarization results reveal that the synthesized polymer acts as a hybrid-type inhibitor. The adsorption of inhibitory atoms of the polymer on the C- steel surface followed Langmuir isotherm. SEM and EDX assure the development of PABITC adsorbed film on the C- steel surface. Quantum calculations were carried out to elucidate the reactive sites in PABITC. All the results approve that PABITC makes a resistive layer to shrink the corrosion process.