This study used a five-turn copper pulsating heat pipe (PHP) for experimental analysis. Water and cerium oxide nanofluid (10 nm and 30 nm particle size) with 0.1% wt concentration was used as carrier fluid at 50% filling ratio. Unsteady state experimental analysis was done to know the effect of carrier fluid and evacuation pressure at different heat loads. The behavior of pulsating heat pipe is evaluated as start-up pulsation, thermal resistance, and effective thermal conductivity with heat load increment. The lowest thermal resistance and highest effective thermal conductivity were observed with cerium oxide nanofluid (10 nm) at lowest 0.0799 bar of evacuation pressure. Effective thermal conductivity at 0.0799 bar is 1.5–3 times better than at 1.01325 bar pressure. So optimum performance was observed with cerium oxide nanofluid (10 nm) at 0.0799 bar evacuation pressure.