<p>This paper presents an eco-friendly voltammetric method for the determination of 17β-estradiol (E2) using a lab-made screen-printed electrode modified with graphene quantum dots (GQDs) synthesized by the pyrolysis of citric acid (CA). Screen-printed electrodes (SPEs) were fabricated using a conductive ink formulated by mixing nail polish with graphite powder, which was then applied onto an acetate sheet substrate. The electrodes were modified with GQDs synthesized by three different methods:&#xa0;CA pyrolysis, hydrothermal synthesis, and microwave-assisted synthesis, to evaluate and compare their electrochemical performance for E2 determination. The SPE modified with GQDs synthesized by the pyrolysis of CA (SPE-GQDs-CAPy) exhibited an electrocatalytic activity with an E2 oxidation peak at 0.6&#xa0;V (vs. the silver ink pseudo-reference electrode integrated in the SPE), using a 0.04&#xa0;mol L⁻¹ BR buffer at pH 2.0, as supporting electrolyte. The analytical curve obtained for E2 showed a linear concentration range between 5.0 and 100.0 nmol L⁻¹, with a limit of detection of 2.4 nmol L⁻¹. The proposed electroanalytical method was applied in addition and recovery studies using water samples from Lake Igapó II (Londrina–PR) and synthetic urine, showing recoveries of approximately 98%. Pharmaceutical formulations containing E2 were also analyzed, and the results were in agreement with those obtained using a comparative method (HPLC), at a 95% confidence level. Thus, the electroanalytical method developed using SPE-GQDs-CAPy represents a simple and effective alternative for the quantification of E2 or total estrogens in environmental, biological, or pharmaceutical samples. Additionally, the proposed method demonstrates a more environmentally friendly profile compared to HPLC, as evaluated using AGREE software. It is simple, rapid, does not require toxic solvents, consumes less energy, and enables the possibility of online or in situ analysis.</p> Graphical Abstract <p></p>