This paper describes the thermal analysis of building block used for passive cooling application. For this purpose, a concrete block with cavities, drilled near the outer wall, is filled with micro encapsulated Phase Change Material (PCM). The commercially available PCM, HS 29 is used for this analysis. The micro encapsulated PCM filled in the cavities and during the heating cycle, The PCM absorbs latent heat and melts. This will prevent the heat entry into the living space and hence cool the space. The thermal performance of the brick is analyzed by Ansys-Fluent 14.5. The two-dimensional numerical analysis has been carried out using finite element analysis by seeing heat and mass transfer in the PCM. The effectiveness of PCM in the building bricks has been estimated by relating three different brick types, viz, normal solid bricks with air filled in the cylindrical cavity and bricks with PCM filled in the cylindrical cavity. In this case, the PCM filling holes are offset from center of the brick towards the exposed surface to reduce the re-entry of heat during solidification cycle. From the analysis is found that brick filled with PCM is more effective for reduction in heat flux while using for passive cooling application of buildings. © 2020 Author(s).