The buildings of river-bed hydroelectric power plants are located in the riverbeds. The pressure walls of their machine halls work together with the ceilings of the machine halls, forming the main load-bearing structure of the hydroelectric power plant building, which carries of loads. The run-of-river buildings of hydroelectric power plants and the pressure buildings of pumped storage power plants have significant similarities with each other, including the same main load-bearing reinforced concrete structures, primarily the pressure headwalls of the machine halls and the pressure shield walls with abutment against the floors. Belonging to the class of massive hydraulic structures, the pressure walls and ceilings of the machine halls of the river-bed hydroelectric power plant buildings (shield walls of pumped storage power plant buildings) consist of separate blocks separated by inter-block construction seams. Compared to monolithic structures, the weakened inter-block construction joints cause cracks that reduce the strength and operational reliability of the entire hydroelectric power plant/PSPP, making it difficult to repair using traditional methods. In order to experimentally substantiate the strengthening of reinforced concrete structures of the hydroelectric power plant with external reinforcement using composite carbon materials, a set of laboratory studies was conducted on reinforced concrete models of a fragment of the pressure wall of the machine hall of the run-of-the-river building of the hydroelectric power plant, at a scale of 1:15. Some models were without reinforcement, while others were reinforced with external reinforcement made of composite carbon tape. As a result of the laboratory studies, it was established that the system of external reinforcement from composite carbon tapes contributes to a decrease in the opening width of inter-block construction joints a_(cr, ш) and tensile stresses in the working steel reinforcement σ_(s, ш), displacements f of the top of the models; the occurrence of tensile stresses σ_(f) in the reinforcing element (composite carbon tape); while the failure load of the reinforced model increases in comparison with the non-reinforced model. Consequently, the conducted research allowed us to experimentally substantiate the effectiveness of strengthening the pressure walls of hydroelectric power plant turbine halls with external reinforcement made of composite carbon strips. Consequently, the conducted research allowed for the experimental justification of the effectiveness of reinforcing the pressure walls of hydroelectric power plant machine rooms with external reinforcement made of composite carbon tapes.