Thermo-optic coefficients dn/dT were determined for orthorhombic BeAl6O10 crystal for light polarizations E || Np, Nm and Ng in the wavelength range of 0.4–1.1 m. Thermo-optic dispersion formulas for principal thermo-optic coefficients of BeAl6O10 are presented for this spectral range. The principal dn/dT are positive and show a polarization-anisotropy: dnp/dT = 6.4, dnm/dT = ...