This paper examines, the thermal performance of 20 different mortar mixes, which were prepared in order to study the behaviour of mortar incorporating Phase Change Materials (PCM). The PCM were was used at a rate of 10, 20 and 30% by weight of total solid materials. Silica fume was added to the mixes by 10, 20, 30 and 50% by weight of cement to enhance the mortar properties. Mortars which incorporate phase-change materials (PCM) have the capability to help regulate the temperature inside buildings, contributing to the thermal comfort while decreasing the amount of mechanical heating and cooling energy required, therefore they have the potential to reduce building carbon emissions. The mechanical characteristics and physical properties of the mortar with PCM were studied. The results show that mortar with Phase Change Materials up to PCM20% can be used with an optimal compressive strength. Silica fume (SF), up to a 20% SF addition, enhanced the mechanical properties of the mortar.