Abstract In this paper, we produced new kind cement mortars with thermal energy storing/releasing properties, containing silica fume (SF)/capric acid-stearic acid eutectic mixture (CA-SA) as form-stable composite phase change material (FSC-PCM). The physicochemical compatibility between CA-SA eutectic PCM and SF was studied by fourier-transform infrared (FTIR), X-ray powder diffraction (XRD) and scanning electron microscope (SEM) techniques. The differential scanning calorimetry (DSC) results indicated that the FSC-PCM including 37 wt% CA-SA eutectic PCM has a phase change temperature and latent heat capacity of 23.28 °C and 65.6 J/g, respectively. Thermogravimetric (TG) measurements and thermal cycling examination demonstrated that FSC-PCM has great stability in terms of its chemical structure, thermal degradation and cycling reliability in LHTES properties. To achieve novel type cementations composite mortar, the FSC-PCM was replaced with ordinary cement mortar (OCM) in weight fraction of 10%, 15% and 20%. Thermoregulation performance test showed that the maximum indoor temperatures differences between the OCM and latent heat storage-cement mortar (LHS-CM) based rooms were found as 2.48 °C during the heating stage and 1.71 °C during the cooling stage. Mechanical test findings of the LHS-CMs showed acceptable mechanical properties and have suitable properties for regulation of indoor temperatures and reducing energy consumption in buildings.