3-Phenylamino-4-phenyl-1,2,4-triazole-5-thione was synthesized and characterized by elemental analysis, IR and X-ray single crystal diffraction. Density functional theory calculations of the structure, natural bond orbitals, atomic charge distributions and thermodynamic functions of the title compound were performed at B3LYP/ 6-311G** and PBE1PBE/6-311G**levels of theory, respectively. NPA atomic charge distributions indicate that the title compound can be used as a potential multi-dentate ligand to coordinate with various metallic ions. Calculation of the second order optical nonlinearity was also carried out. The thermodynamic properties of C(0)(p,m), S(0)(m) and H(0)(m) were calculated and correlative equations between the thermodynamic properties and temperatures were also obtained.