The main aim of the research was to investigate the electrochemical properties of serotonin in two solvents using cyclic and differential pulse voltammetry. The influence of pH, speed of electrode polarization and concentration of serotonin on its redox properties was investigated and the possible adsorption of serotonin on the surface of the working electrode was investigated. Cyclic voltammetry showed an increase in the potential and current peak with increasing electrode polarization speed, and such a process is under mixed adsorption and diffusion control. By means of differential pulse voltammetry, it was determined that the height of the oxidation current peak of serotonin decreases with successive recording of the voltammogram, which indicates that the oxidation product of serotonin is adsorbed on the surface of the working electrode. In addition, the pH values for the oxidation of serotonin in an ethanol solution at pH=9 and in an aqueous solution at pH=5 were determined. It was also determined that the height of the oxidation current peak increases with increasing concentration and that the current of the oxidation current peak depends linearly on the concentration in the concentration range from 1⸱ 10-6 mol dm-3 to 1⸱ 10-4 dm-3 for an alcoholic solution of serotonin and from 1∙10-6 mol dm-3 to up to 9 10-5 mol dm-3 for aqueous solution of serotonin. Thesis