Abstract: High-entropy design provides an effective strategy for enhancing the comprehensive performance of thermal/environmental barrier coatings (T/EBCs) for hot-section components of aero-engines. In this study, γ−Er₂Si₂O₇ and the high-entropy rare-earth disilicate ceramic γ−(Ho_0.2Er_0.2Tm_0.2Y_0.2Yb_0.2)₂Si₂O₇ were synthesized via a solid-state reaction method. Their phase composition, microstructure, mechanical properties, thermophysical behavior, and long-term high-temperature stability at 1 300–1 500 ℃ were systematically investigated using X ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser flash analysis, and high-temperature sintering tests.The results indicate that the as-prepared γ−(Ho_0.2Er_0.2Tm_0.2Y_0.2Yb_0.2)₂Si₂O₇ high-entropy ceramic possesses a homogeneous single-phase γ structure. Compared with Er₂Si₂O₇, the high-entropy ceramic exhibits lower porosity, higher Vickers hardness, superior fracture toughness, and lower thermal conductivity. Thermal conductivity values of γ−(Ho_0.2Er_0.2Tm_0.2Y_0.2Yb_0.2)₂Si₂O₇ are 0.933 W•m⁻¹•K⁻¹ at 1 000 ℃ and 1.640 W•m⁻¹•K⁻¹ at 1 500 ℃, respectively. After sintering at 1 300 ℃ and 1 500 ℃ for different durations, γ−(Ho_0.2Er_0.2Tm_0.2Y_0.2Yb_0.2)₂Si₂O₇ exhibits a low grain-growth rate, demonstrating excellent resistance to high-temperature sintering. The synergistic effects of configurational entropy, lattice distortion, and sluggish diffusion contribute to the enhanced densification, mechanical reliability, thermal-insulation capability, and sintering resistance of γ−(Ho_0.2Er_0.2Tm_0.2Y_0.2Yb_0.2)₂Si₂O₇. These results elucidate the intrinsic structure–property relationships of the high-entropy rare-earth disilicate γ−(Ho_0.2Er_0.2Tm_0.2Y_0.2Yb_0.2)₂Si₂O₇ and demonstrate its potential as a highly promising candidate material for advanced T/EBC applications.