A new octahedral pyridine-phosphonodithioato nickel(II) complex ([(RO)(R)PS2Ni(py)(2)], R = p-methoxyphenyl-; OR = 3-methyl-1-butoxy-; py = pyridine] was synthesized and elucidated by elemental analysis, MS, vibrational spectroscopies (FTIR and Raman). The single crystal of the compound has been prepared and characterized by single crystal X-ray diffraction. The empirical ground state electron density distribution of [(RO)(R)PS2Ni(py)(2)] obtained by X-ray crystallography was compared with the theoretical counterpart predicted by density functional theory (DFT) with B3LYP/LANL2DZ level. Moreover, the geometrical structures, atomic charges, frontier molecular orbitals, molecular electrostatic potential (MEP) surfaces and nonlinear optical (NLO) properties were studied by using DFT. (C) 2019 Elsevier B.V. All rights reserved.