In this paper, a highly sensitive, reagentless, electrochemical strategy is reported for the detection of a cancer biomarker-Vascular Endothelial Growth Factor (VEGF). Disc shaped carbon fiber microelectrodes were used as the immunosensor platform. Ferrocene monocarboxylic acid labeled anti-VEGF was covalently immobilized on the microelectrode surface using a Jeffamine cross-linker. The formation of immunocomplexes leads to a decrease in the electrochemical signal of ferrocene monocarboxylic acid owing to increased spatial blocking of microelectrode surface. These signal changes enable quantitative detection of VEGF in solution. Voltammetric measurements were conducted to evaluate the interfacial immunoreactions and to quantitatively detect VEGF biomarker. The proposed immunosensing strategy allows a rapid and sensitive means of VEGF analysis with a limit of detection of about 38 pg/mL. This opens up the possibility of employing these electrodes for various single cell analysis and clinical applications. Further, experimental conditions such as concentration of the immobilized antibodies and incubation period were optimized. Following this, the stability and specificity of the immunosensors were also evaluated.