To investigate the effect of heterogeneous phases on the thermal-mech. properties and calcium-magnesium-aluminum-silicate (CMAS) corrosion resistance of multi-component disilicate ceramics, four different compositions of (Sc0.33Er0.33Yb0.34)2Si2O7 ceramics were prepared using the solid-phase reaction method with different rare-earth to silicon molar ratios in the raw materials.The (Sc0.33Er0.33Yb0.34)2Si2O7 ceramics containing (Sc0.33Er0.33Yb0.34)2SiO5 heterogeneous phases showed lower thermal conductivity and hardness but higher bulk ceramic densification, stability of grains at high-temperature, thermal expansion coefficients, and Young′s modulus.However, the (Sc0.33Er0.33Yb0.34)2Si2O7 ceramics with SiO2 heterogeneous phases exhibited lower thermal expansion coefficients, hardness, and Young′s modulus but higher densification, stability of grains, and thermal conductivityFurthermore, the ceramics containing SiO2 heterogeneous phases showed better resistance to CMAS corrosion, which isolated CMAS melts effectively from the surface.Compared to Yb2Si2O7, (Sc0.33Er0.33Yb0.34)2Si2O7 exhibits lower thermal conductivity and superior resistance to CMAS corrosion, making it a promising candidate material for multifunctional thermal insulation and environmental barrier coatings (TEBCs).