The emergence of COVID-19 in December 2019 has wrought profound impacts on global health, with nearly 700 million confirmed cases and close to 7 million fatalities reported worldwide by 2023. While the utilization of electrochemical sensors for detecting COVID-19 antigens has shown promise, challenges persist, particularly in sensitivity, selectivity, and cross-reactivity issues resulting from structurally similar viruses, leading to false positives and diminished test accuracy. To address this issue, careful optimization of sensor design and capture agent selection remains important. This study introduces a modified screen-printed graphite electrode (SPCE) incorporating gold nanoparticles (AuNPs) and Staphylococcus protein A, utilizing a sandwich test method for antigen detection. The signal was then measured using the amperometry technique through a reaction between conjugated HRP and luminol. Successful electrodeposition of AuNPs onto the electrode surface enhances electrochemical signal and sensor sensitivity. Nonetheless, electrochemical impedance spectroscopy (EIS) confirms successful electrode step-by-step modification. Functional experiments demonstrate the sensor’s efficacy in detecting COVID-19 N-protein with calculated limits of detection (LODs) of 4.02 pg.mL−1 and limits of quantification (LOQs) of 13.4 pg.mL−1. While initial results are promising, further clinical validation is important to access the sensor’s practical utility in real-world scenarios, marking a crucial next step in this study. Also, the stability and specificity test will be conducted to prove the ability of the biosensor to detect COVID-19 N-Protein without any cross-reactivity with other viruses for an amount of time. In addition, this study provides a basis and reference values to improve this sensor for detecting other patient samples in the future.