Present study investigates the heat sink involving solid and hollow fins to improve the performance of cooling system involving phase change material (PCM). Three-dimensional numerical simulations are performed employing Ansys fluent software. Various heat sink (HS) configurations, namely HS with circular and square solid fins and HS with circular and square hollow fins, are studied in a view of augmenting the operation time of modern electronics without overheating. The effect of natural convection is taken into account in the numerical simulation, which is based on Boussinesq approximations. Transient numerical simulation is carried out using the finite volume method (FVM) with organic PCM (paraffin wax), which has a phase change transition in the range of 58-62 °C. Heat inputs are supplied on the HS bottom surface in the range of 1.0-2.0 kW/m², which impersonate the heat rejected by various electronic components housed inside the electronic devices. Numerical results indicate that hollow fins embedded with PCM improve the performance of the HS by reducing the HS base temperature.