TlGaS 2 single crystal were grown by using the Bridgman method. The deep levels of TlGaS 2 single crystal were investigated by the TSC (thermally stimulated current) and PlCTS (photoinduced current transient spectroscopy) techniques. The activation energies of the four peaks observed from the TSC curve are (a) 0.18, (b) 0.23, (c) 0.36, and (d) 0.66 eV. Peaks a and b are located below the conduction band and peaks c and d are located above the valence band. The escape frequencies are calculated to be 2.9 × 10 6, 1.8 × 10 7, 3.4 × 10 7, and 5.6 × 10 10 s −1, respectively. The PICTS spectra of TlGaS 2 single crystal show four deep traps whose activation energies are calculated to be 0.17, 0.23, 0.35, and 0.65 eV, respectively.