Optically transparent glass-ceramics (40BaO-20TiO(2)-40SiO(2) (mol%)) consisting of nonlinear optical fresnoite Ba2TiSi2O8 (BTS) nanocrystals (diameter: 100-200 nm) are fabricated, and their elastic properties and deformation behavior are examined as a function of the volume fraction (f) of BTS nanocrystals using cube resonance and Vickers indentation techniques. The elastic properties such as Young's modulus (E) increases linearly with increasing the volume fraction of nanocrystals, e.g., E = 84 GPa for f = 0% (glass) to E = 107 GPa for f = 54.5%. The Vickers hardness (H-v) and indentation fracture toughness (K-c) increase from 5.0 to 6.0 GPa for H-v and 0.48 to 1.05 MPa m(-1/2) for K-c with increasing the volume fraction (from f = 0% to f = 54.5%), but they do not change linearly against the volume fraction of nanocrystals. It is suggested that BTS nanocrystals themselves induce a high resistance against deformation during Vickers indenter loadings. (C) 2011 Elsevier Ltd. All rights reserved.