The influence of the experimental conditions (glutathione concentration and incubation time and temperature) concerning the covalent immobilization of glutathione via carbodiimide coupling on the behavior of a glutathione modified screen-printed carbon electrode obtained by electrografting is evaluated. The optimized parameters fasten the modification process and improve the performance of the sensor as compared to the usual procedure. This suggests the convenience of a tailored preparation of metal sensors based on metal-binding biomolecules such as glutathione.