Sulphur doped graphitic carbon nitride (S_GCN) was effectively prepared and comprehensively described. A straightforward synthetic process based on thermal condensation was reported for the synthesis of S_GCN using thiourea as a precursor. Cyclic voltammetry (CV) and differential pulse voltammetry were used to evaluate the electrochemical performance of cortisol. S_GCN sheets were used to boost the electro-catalytic activity, exhibiting very exceptional electrochemical behaviour towards cortisol. As a result, we obtained a broad linear response range of 0.1–100 μM, as well as a comparatively low detection limit (15.8 × 10⁻⁸ M). Furthermore, the fabricated S_GCN/CFP electrode shows excellent selectivity in the presence of a large number of possible interfering species. S_GCN comprises (C with N and S) heteroatoms, which most likely would have led to a better current response towards cortisol detection. Furthermore, the structural defects that generate additional active sites on the surface of S_GCN may enhance the quick electron transfer that occurs during the oxidation of cortisol.