In recent studies, it has been noticed that adding nanoparticles into the working fluid as a suspension improves the thermophysical properties of the nanofluids produced. In the test setup manufactured for this study, hexagonal boron nitride (h-BN) in lamellar structure at 1%, 1.5%, and 2% concentrations and surfactant Triton X-100 at 0.5 vol.% were used. Nanofluids containing h-BN nanoparticles and deionized water as the working fluid were produced, and these fluids were experimentally investigated on the prepared heat pipe experimental setup. During the experiments, temperature changes in the heat pipe and the related improvements in efficiency, as well as the thermal resistance and heat conduction coefficient of the nanofluids in the heat pipe, were studied experimentally. The processes in the heat pipe were conducted at a heating power of 200 W, 300 W, and 400 Wand a cooling water flow rate of 5 g/s, 7.5 g/s, and 10 g/s under vacuum operating conditions. It was determined that nanofluids prepared at different concentrations improved the system performance. The highest efficiency of the heat pipe was found to be 96.81% in the study performed at 1% concentration, 400-W power of the heater, and 5 g/s flow rate. Parameters with the highest efficiency improvement rate were obtained with 400-W heating power, 7.5 g/s flow rate, and 1% concentration of h-BN/deionized water nanofluid. It was observed that in the heat pipe the heat transfer coefficient increased by 44.36%, and the thermal resistance of the system was reduced by 30.73% with the use of nanofluids prepared with nanoparticles.