Single crystals of the layered compound TlInS2 were grown by direct synthesis of their constituents. The spectral and optical parameters have been determined using spectrophotometeric measurements of transmittance and reflectance in the wavelength range 200-2500 nm. Absorption spectra of thin layers of TlInS2 crystals are used to study the energy gap and the interband transitions of the compound in the energy region 2 – 2.4 eV. The direct band gap were determined to be 2.34 eV. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal one in the transmitted region. Photoconductivity measurements at room temperature show that both dark and photocurrent increase linearly with the applied voltage. The average energy gap obtained from the spectral dependence of the photocurrent determined to be 2.32 eV.