A new simple and reliable in-situ mercury film sensor coupled with affinity differential pulse stripping voltammetry (ADSPV) or affinity cyclic voltammetry (ACV) was investigated. The interaction of fenoprofen with bovine serum albumin (BSA) onto the proposed electrochemical sensor was studied. The nature of the electrochemical process of fenoprofen by cyclic voltammetry was depicted. Reproducibility of the proposed method was checked giving a precision of 0.073 standard deviation. The limit of detection and limit of quantification were 7.0 and 22.0 nmol/L, respectively. Fenoprofen was interacted with BSA by 1:1 stoichiometry to form electroinactive supramolecular complex. The binding constant was precisely estimated by non-linear regression analysis based on the shifting of analyte peak potentials. The proposed experiments and data analysis could be used to investigate the drug-protein binding constant within a short analysis time compared to other chromatographic techniques.