The transmittance and absorption spectra of a high-quality Zn 2 TiO 4 single crystal have been measured along the a-axes at room-temperature in the range of 200-1000 nm. The wavelength dependent refractive index, extinction coefficient, real and imaginary parts of the complex dielectric constant of the Zn 2 TiO 4 crystal have been derived from the measured T and α spectra. By fitting the refractive index spectrum, the Sellmeier dispersion equation of the Zn 2 TiO 4 crystal has been obtained. The validity of Cauchy-Sellmeier equation has been evaluated in the energy range of 2.90-3.20 eV representing the Urbach tail. Applying the singleeffective oscillator model, the dispersion energy E d and the oscillator energy E 0 have been determined as 18.76 and 5.05 eV, respectively. The obtained dispersion energy E d takes on ionic crystal value.