An organic-inorganic hybrid complex based on Cissus quadrangularis (CQ) plant extract and zirconium acetate (CQ-ZrAc) was synthesized, characterized and studied as a novel green inhibitor against mild steel corrosion in 1 M HCl solution using gravimetric analysis, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The corrosion inhibition effect of the complex was also compared with CQ. GC-MS and FTIR studies were conducted to assess the active organic species and the functional group present in the extract which caused its adsorption on the mild steel surface and lead to complex formation with ZrAc. The gravimetric parameters revealed that inhibition efficiency depends both on the temperature of corrosive solution and inhibitors concentration. Adsorption of both CQ and CQ-ZrAc follow Langmuir adsorption isotherm. PDP analysis suggests that both compounds act as a mixed type of inhibitor. EIS data revealed the formation of a protective film by the adsorption of active species present in the extract. SEM images show better morphology in presence of CQ-ZrAc complex as compared to CQ. UV-visible and FTIR results indicate a good interaction between inhibitors and mild steel surface. Density functional theory has been carried out to correlate the inhibition efficiency with inherent molecular structure and parameters. Analysis of variance statistically compare the difference existing between inhibition efficiencies from gravimetric, PDP and EIS technique and suggests that they are not significantly different.