A new electrochemical sensor (BT-I/GC) was prepared for the determination of tartrazine (TRZ) by modifying the glassy carbon (GC) electrode with 1,3,4-thiadiazoleidine-2,5-dithiol (Bismuthiol I, BT-I). The characterization of the prepared sensor was carried out by some electrochemical techniques and Fourier transform infrared spectroscopy (FT-IR). The rapid and simple determination of TRZ was performed on the surface of the BT-I/GC sensor by differential pulse voltammetry (DPV) technique. Under the optimum experimental conditions, linear working ranges for TRZ detection were found as 38.5 nM-3.72 μM, 3.72 μM-24.10 μM, and 24.10 μM-307 μM, and the value of the limit of detection (LOD) was found as 9.8 nM. The fabricated sensor was used successfully to detect TRZ in soft drink and energy drink samples with recovery values between 95.8 % and 103.8 %.