Efficient, clean and quiet thermal management has become a vital challenge in for cooling of electronic devices. To enhance the capability and efficiency of passive thermal management, novel composite materials have been designed by the combination of graphene nanoplatelets (GNPs), multiwall carbon nanotubes (MWCNTs), aluminium oxide (Al2O3) and copper oxide (CuO) dispersed in the RT-28HC used as a phase change material (PCM). The series of mono and hybrid nano-enhanced phase change materials (NePCMs) were synthesized using constant mass fraction of 1.0 wt% of each type of nanoparticles to establish the optimum NePCM in terms of thermal properties for deficient thermal management of microelectronics. Various material characteristic techniques such as ESEM, FT-IR, XRD, TGA, DTG, DSC, IRT and thermal conductivity apparatus were used. The microstructure, chemical composition, crystallinity, thermal and phase-change heat transfer characteristics were investigated extensively for each sample of NePCM. The results showed the good chemical and thermal stability of all NePCMs without changing the chemical structure of RT-28HC. The surface morphology and crystal formation analysis revealed the uniform dispersion of nanoparticles onto the surface of RT-28HC. In comparison of mono and hybrid NePCMs, the results showed that the hybrid NePCM of GNPs/MWCNTs at mass percentage ratio of 75%/25% had the highest thermal conductivity enhancement of 96% compared to the pure PCM having optimum value of phase-change enthalpy of 245.18 J/g. Finally, enhancement in phase transition while melting and thermal properties evidenced that hybrid NePCMs can be used as potential candidate for the thermal management of microelectronics.