This paper investigates the heat transfer and pressure drop characteristics of mango bark-CO2 nanofluid. The physical model comprises flow in a pipe under a constant heat flux of -10W/m 2 . The inclination angle varies between -90 o and +90 o , and volume fraction between 0% and 2.0% for Reynolds numbers of 50 and 100. The numerical code is validated using three research studies on heat transfer coefficient, Nusselt number, and pressure drop. Results show that the heat transfer coefficient and pressure increase with nanofluid volume concentration and Reynolds number. However, the heat transfer coefficient varies nonlinearly with the inclination angle and has a maximum occurring when the inclination angles are -30 o and +60 o while the pressure drop is relatively constant.