Sunset Yellow (SY) is an azo dye used in various food and pharmaceutical industries that deserves special attention because of its allergic and carcinogenic properties. Recently, electrochemical techniques have come to the spotlight because of their high sensitivity, simplicity and rapidity as compared to other techniques. In this work, we have developed a cost‐effective and stable electrochemical sensor by a simple method using Vitamin B12‐derived cobalt oxide coupled with g‐C3N4 (V12‐CoO/gCN) modified Au electrode. The composite prepared for the sensor was characterized using techniques such as FTIR, Powder XRD, SEM analysis, EDAX, and mapping. For electrochemical sensing of the dye Sunset Yellow, CV, DPV, and LSV techniques have been used, out of which DPV shows a better detection limit of 1.39 nM followed by LSV and CV that displayed detection limits of 3.3 nM and 4.14 nM respectively. When 5 real samples obtained from the local market are analyzed using the DPV technique, the detection limit is obtained in the range between 2.1 nM and 6.9 nM. This method leads to the development of an electrochemical sensor for the detection of Sunset Yellow to get a lower detection limit that can be used in food toxicology and related fields.