Yb2SiO5 is a promising material for thermal/environmental barrier coatings (T/EBCs), and its mechanical and thermal properties, which are essential to the coating design and applications, are investigated in this work. Yb2SiO5 has relatively high fracture toughness, bending and compressive strength, but low Young's modulus. It is also tolerant to damage, which is underpinned by grain delamination and cleavage along {100}, {001}, and {040} planes. The average linear coefficient of thermal expansion (CTE) is 6.3 x 10(-6) K-1 (473-1673 K) and the anisotropic CTEs are: (a) = (2.98 +/- 0.16) x 10(-6) K-1,(b) = (6.51 +/- 0.19) x 10(-6) K-1, and (c) = (9.08 +/- 0.16) x 10(-6) K-1. The thermal conductivities are 2.3 and 1.5 W (mK)(-1) at 300 and 1200 K, respectively. The unique combination of these properties warrants Yb2SiO5 promising for T/EBCs applications.