In this paper, we report the development of an electrochemical immunosensor with a direct signal generation scheme. To achieve this, ferrocenecarboxylic acid was conjugated as an electroactive label to an immunocomplex immobilized on an electrochemically pretreated glassy carbon electrode. The pregnancy hormone and tumor marker, human chorionic gonadotrophin (hCG), was employed as a model analyte. Direct oxidation of ferrocenecarboxylic acid facilitated a signal generation scheme for the quantification of hCG at the immunosensor. Evaluation of the immunosensor performance has yielded statistically acceptable agreement in hCG levels present in several human serum samples compared to those reported by a Sydney hospital.