Biosensors are devices used to detect biomolecules or their derivatives. The most important performance factors used to evaluate biosensors are sensitivity, specificity, and limit of detection. Miniaturization of biosensors is also a critical point in the literature. With increasing advances in this field, microchips have been used in advanced biosensor technology for full-scale diagnostics and point-of-care diagnostics, with features such as low-cost and high-speed diagnostic [1]. Microchips are a powerful tool for performing quantitative analysis of a wide variety of objects as they have many advantages such as high sensitivity, short analysis time, less sample consumption, high throughput, and low cost. Navarro-Nateras and colleagues used pencil graphite electrodes (PGE) to monitor glucose under cell culture conditions in a microfluidic device [2]. Prasertying et al. applied the pencil tip electrode modified with manganese oxides (MnOxides/PE) as a glucose sensor for amperometric detection in Flow Injection Analysis (FIA) systems [3]. In our study, the response of the anti-CEA modified pencil graphite electrode (Anti-CEA@PGE), intended to be used in microchips, against CEA in a standard electrochemical cell (Ag/AgCl reference electrode and platinum counter electrode) was examined. The analytical performance of the biosensor was examined by optimizing the concentration of anti-CEA and CEA incubation time, and the LOD and working range were determined within the scope of this study. Also, the selectivity and repeatability studies were performed.