This work proposes the development, characterization and modelling of new eco-friendly building walls integrating stabilized forms of phase change materials. The aim is to enhance the hygrothermal and energy performances of buildings by improving their management of thermal energy throughout the year and meeting users’ thermal comfort requirements. These are essential axes to help decarbonize heating and cooling, to rehabilitate buildings and to contribute to the energy transition. The experimental and numerical hygrothermal performances of two different building walls are assessed and compared under realistic weather conditions. The maximum temperature inside the wall is reduced by 2 °C for the phase change material hemp concrete compared to the reference hemp concrete in a context of typical summer heatwaves day. Both phase change material hemp concrete and reference hemp concrete showed good moisture regulation capability by dampening cyclic variations in outdoor humidity. The developed numerical model exhibited a good agreement with the experimental results with a maximum root mean square error between experimental and numerical results of about 0.6 °C and 6% for temperature and relative humidity, respectively.