The present research work investigates the effect of CuO nanoparticles on the nucleate boiling heat transfer characteristics of Isobutane (R600a) refrigerant. All the pool boiling experiments are carried with both pure and nano-refrigerants of 0.01, 0.025, 0.05 and 0.1 percentage by volume. The heat flux is varied from 2 kW.m -2 to 20 kW.m -2 at a regular interval of 2 kW.m -2 . The heat transfer coefficient values for the pool boiling condition of R600a refrigerant are calculated experimentally, which are less deviating from the established theoretical correlations. The added CuO nanoparticles significantly influenced the nucleate boiling heat transfer coefficient of R600a refrigerant at higher heat flux values. The experiment results reveal that the thermophoretic mobility of nanoparticles play a major role in nanofluids heat transport. In the present work, CuO nanoparticles addition in R600a is optimized and is justified based on gravity and agglomeration effect. © 2019, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature.