The transient thermal storage characteristics in a partitioned enclosure filled with microencapsulated phase change material (MEPCM) particles were investigated experimentally and numerically in details. The core phase change materials of the MEPCM are n-octadecane with melting temperature about TM= 28°C and 37°C and filled at the upper and lower partitions in an enclosures. The enclosure is partitioned and is differentially heated by the two horizontal isothermal surfaces, while the other vertical surfaces are considered thermally insulated. The studies have been undertaken for different hot and cold wall temperatures imposed across the enclosure. The consequents show that the numerical results are in agreement with the measured data. Predictions show that at the initial transient, the net energy storage in enclosure, Qnet, increases with the time Fo. Finally, the Qnet approaches quickly the steady state for the case with a higher temperature difference of Th-Tc.