An electrochemical impedance immunosensing method for the detection and quantification of C-reactive protein (alpha CRP) in phosphate buffered saline (PBS) is demonstrated. The protein antibody, Ab-alpha CRP, has been covalently immobilized on a platform comprising of electrochemically deposited 3-mercaptopropionic acid-capped gold nanoparticles Au(MPA)-polypyrrole (PPy) nanocomposite film of controlled thickness onto an indium tin oxide-coated glass plate. The free carboxyl groups present on the nanocomposite film have been used to site-specifically immobilize the Ab-alpha CRP biomolecules through a stable acyl amino ester intermediate generated by N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide hydrochloride and N-hydroxysuccinimide. The nanocomposite film was characterized by atomic force microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and electrochemical techniques. The bioelectrode was electrochemically analyzed using modified Randles circuit in terms of constant phase element (CPE), electron transfer resistance (R (et)), and Warburg impedance (Z (w)). The value of n, a CPE exponent used as a gauge of heterogeneity, for the Au-PPy nanocomposite film was found to be 0.56 which is indicative of a rather rough morphology and porous structure. A linear relationship between the increased a dagger R (et) values and the logarithmic value of protein antigen, Ag-alpha CRP, concentrations was found in the range of 10 ng to 10 mu g mL(-1) with a R (et) sensitivity of 46.27 a"broken vertical bar cm(2)/decade of [Ag-alpha CRP] in PBS (pH 7.4).