Anisotropic mechanical properties of KSr2Nb5O15 (KSN) crystals were investigated through first-principles calculations based on density functional theory. These properties were experimentally verified via nanoindentation on textured KSN ceramics fabricated, using a reactive template grain growth method. Nanoindentation was performed in directions parallel and perpendicular to the [001] direction of samples consisting of highly oriented grains with tetragonal symmetry. Calculations revealed that Nb-O yields a relatively strong covalent effect and Nb-O octahedral distortions induce spontaneous polarization in the KSN crystal. The measured indentation modulus values concurred with the predictions, based on the calculated elastic constants, as indicated by an anisotropic ratio of similar to 10% between the 2 tested orientations. The hardness exhibited negligible anisotropy. However, the predictions revealed a pronounced anisotropy of the Young's modulus (ratio of similar to 40% between the [100] direction and a direction tilted by similar to 45 degrees from the [001] toward the [100]).