The crystalline nickel(II) di-i-amyl) dithiophosphate (Dtph), [Ni{S₂P(O-i-C₅H₁₁)₂}₂] (I) was isolated on a preparative scale and characterized by ¹³C, ³¹P MAS NMR, and X-ray diffraction (CIF file CCDC no. 1469369). The χ²-statistic diagrams were constructed from full ³¹P CP/MAS NMR spectra for calculating the ³¹P chemical shift anisotropy: δ_aniso = δ_zz–δ_iso and the asymmetry parameter η = (δ_yy–δ_xx)/(δ_zz–δ_iso). The key structural unit of I is the centrosymmetric [Ni{S₂P(O-i-C₅H₁₁)₂}₂] molecule in which the nickel atom coordinates two Dtph ligands in the isobidentate fashion. In molecule I, each carbon, oxygen, and sulfur atom is statistically disordered over two sites with equal occupancies. However, the disorder does not affect nickel and phosphorus. These results were interpreted as the presence in I of two [Ni{S₂P(O-i-C₅H₁₁)₂}₂] molecules rotated through 21.0(1)° (the angle between the [NiS₄] chromophore planes) relative to each other around the bisecting P–Ni–P axis passing through both four-membered [NiS₂P] rings. The two molecules occupy crystal lattice sites with equal probabilities. The thermal behavior of I was studied by simultaneous thermal analysis under argon. The course of the thermal destruction of the complex was established, nickel pyrophosphate (Ni₂P₂O₇) was identified as the final product of thermal transformations.