In this work, a two-dimensional numerical model has been developed to study the thermal performance of a cylindrical heat pipe utilizing nanofluids. Al2O3-water based is considered as the working fluid. The numerical model represented as steady-state incompressible flow. The governing equations in cylindrical coordinates have been solved in vapor region, wick structure and wall region, using finite deference with forward-backward upwind scheme. A substantial change in the heat pipe liquid pressure drop, temperature difference, maximum heat transfer limit, capillary pressure and thermal resistance is observed when using a nanofluid. The nanoparticles within the liquid enhance the thermal performance of the heat pipe by reducing the thermal resistance and temperature difference by 0.168 K/W and 5.06 K respectively. While increasing the maximum heat load and the capillary pressure by 96 W and 192.46 Pa respectively. All these results at input heat of 30 W and nanoparticles concentration of 5 Vol. %.The results of wall temperature distribution for the heat pipe have been compared with the previous study for the same problem and a good agreement has been achieved