In this study, the potential application of expanded vermiculite (EVM) as the supporting material and capric–palmitic acid (CA–PA) binary eutectic as the adsorbent mixture to fabricate a form-stable composite CA–PA/EVM by a vacuum impregnation method was investigated. The prepared form-stable composite CA–PA/EVM was then characterized by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and a thermal cycling test. The maximum loading capacity and melting enthalpy of CA–PA/EVM could reach 51.84% and 67.5 J g⁻¹. Meanwhile, the thermal physical and mechanical properties of the CA–PA/EVM-based thermal energy storage mortars were examined to determine if the composite material based on the newly invented CA–PA/EVM material can be employed for energy conservation and efficiency in the building field. In addition, the law of full-field deformation evolution of CA–PA/EVM-based thermal energy storage mortar under uniaxial compression failure was studied based on digital image correlation (DIC) technology, which provides certain guiding significance for the application of CA–PA/EVM-based thermal energy storage mortars in practical engineering.