During both hot and cold seasons, masonry walls play an important role in the thermal performance between the interior and the exterior of occupied spaces. It is thus essential to analyze the thermal behavior at the hollow block’s level in order to better understand the temperature and heat flux distribution in its structure and potentially limit as much as possible the heat transfer through the block.In this scope, this paper offers an experimental and numerical in-depth analysis of heat transfer phenomena inside a hollow block using a dedicated experimental setup including a well-insulated reference box and several thermocouples and fluxmeters distributed at the boundaries and inside the hollow block. The block was then numerically 3D modelled and simulated using COMSOL Multiphysics under the same conditions, properties, and dimensions as the experimentally tested block. The comparison between the numerical and experimental results provides very satisfactory results with relative difference of less than 4% for the computed thermal resistance.