The present experimental study reports the thermal performance analysis of a phase change material (PCM)-based finned heat sink placed on a silicone rubber heater which mimics the CPU chip and is cooled by natural and forced convection. The heat sink is subjected to constant and cyclic loading for five input power values (4, 6, 8, 10, and 12W). Paraffin wax and 1-hexadecanol are selected as PCM for this study, which have melting points in the ranges of 58 degrees C-60 degrees C and 48 degrees C-50 degrees C, respectively. The steady-state and transient base temperature behavior of the heat sink indicated that the heat sink with PCM performed better than the heat sink without PCM under natural convection subjected to a constant load. With the increase in input power, the melting time of the PCM is reduced. Between the two PCMs, the heat sink filled with 1-hexadecanol performed better in transient operation. It was observed that cyclic loading offers better insight into the thermal behavior of the heat sinks at different power inputs. The total operation time of heat sink filled with 1-hexadecanol takes less time than paraffin-filled heat sink during cyclic loading when subjected to natural convection. For cyclic loading, the total operation time of the heat sink is reduced by a factor of 0.41 and 0.43 times when cooled by forced convection as compared to natural convection for heat sink filled with paraffin wax and 1-hexadecanol, respectively.