In this paper, thermal performance of a heat pipe has been studied experimentally using 50 nm copper nanoparticles deionized water and acetone based nanofluids. The effect of nanoparticle concentrations (0.5 and 1) on thermal resistance of heat pipe was investigated. Moreover, the effect of angle of inclination on thermal performance of the heat pipe was examined and the average temperature distribution of the heat pipe was recorded too. Regardless of the nanofluid type used, results showed that when the nanoparticles concentration increases, the evaporator section temperature drops whereas the condenser section temperature increases. Furthermore, for the same heat input, the higher the particle concentration, the less the thermal resistance was. It was also observed that the thermal performance of the heat pipe is best at 75° and 45° angles for deionized water based nanofluid and acetone based nanofluid, respectively. © 2020, Springer Nature Singapore Pte Ltd.