Melatonin (N-acetyl-5-methoxytryptamin) is a ubiquitous molecule widely distributed in nature. It is a hormone produced by the pineal gland, which plays a role in the body�s sleep cycles and it is a powerful antioxidant. It is possible to find it in several foods (fruit, rice, corn) and as food supplement. Screen-printed carbon electrode (DRP-150) and graphene modified screen-printed electrode (DRP-110GPH) were tested as sensors for the detection of melatonin using electrochemical detection (differential pulse voltammetry), at different pH values (7.4, 7.0, and 6.4). Quantitative detection of melatonin was possible, with better results when graphene modified screen-printed electrodes were used. The pH influenced the position of the peak as well, with lowering the pH moves more in the right. Both electrodes have been tested on samples of food supplements containing melatonin, with good recovery degrees.