Aim: In this study, it was aimed to determine the reduced Glutathione (GSH) at the modified sensor with a simple and reliable electroanalytical method. Material and Method: Cyclic voltammetry and differential pulse voltammetry techniques were used for the determination of reduced-GSH. And the modified sensor was fabricated by dropping single-walled carbon nanotube (SWCNT) dispersion onto the surface of the glassy carbon electrode. Results: The determination of reduced-GSH was accomplished at SWCNT modified sensor. The relationship between the current responses of the sensor and the concentrations of the reduced-GSH (1.0 x 10-(8) - 5.0 x 10-(8) M) showed excellent linearity and the detection limit was calculated as 75 nM. Discussion: Determination of trace amounts of reduced-GSH in urine samples was successfully applied at the modified sensor. The results showed that modification of the glassy carbon electrode with SWCNT could provide a new strategy for determining the concentration of GSH in physiological solutions.