The objective of this research was to carry out the hydrothermal reduction of graphene oxide (GO) that results in graphene hydrogel (rGO) formation. In the process, olive leaf extract (ELM) was used as a reducer. The objective of this work was also to examine the capacitive properties of rGO hydrogels and to apply them in supercapacitors. In the first step, the hydrothermal reduction of GO to rGO was performed at different pH values (3, 7, 10), with different masses of reducing agent (0.28 g, 2.8 g), at different temperatures (120 °C and 180 °C) and with the presence and without the presence of fillers. The obtained rGO hydrogels were dried and then it was applied to the glassy carbon support. Electrodes with rGO samples were tested by cyclic voltammetry in 0.5 mol dm^-3 Na2SO4 solution. The obtained specific capacitances were 30-185 F g^-1. It has been shown that larger specific capacitance values were obtained by using samples prepared at higher pH values, with a higher amount of ELM and prepared at a higher temperatures. The presence of fillers reduces specific capacity, but not significantly. The hydrogels rGO4, rGO5 and rGO7 were used directly after the synthesis and rinsing in preparin Supercapacitor1, Supercapacitor2 and Supercapacitor3. Prepared supercapacitors were tested by cyclic voltammetry method and 1000 consecutive charge and discharge cycles were carried out. The specific capacities of the supercapacitors are higher compared to the values obtained by using three electrode system experiment, as a result of the porous hydrogel structure. Specific capacities obtained by the cyclic voltammetry range from 111 to 202 F g^-1. The specific capacities obtained from the chronopotentiometry were slightly lower due to the narrow voltage limits used during examination, ranging from 175 to 45 F g^-1. For the supercapacitor, a specific energy of 32.60 kW s kg^-1 to 127.36 kW s kg^-1 was determined. For all tested supercapacitors, capacity, self-discharge resistance and equivalent series resistance have been monitored during charging and discharging. From the obtained results it can be concluded that Superkondenzator3 (rGO7, pH = 3, without filler, m(ELM) = 0.28 g) has the highest specific capacities and the smallest equivalent series resistance resistance, while Superkondenzator1 (rGO4, pH = 10, without filler, m(ELM) =0.28 g) has the highest self-discharge resistance.