The crystal and molecular structure of the 1:1 adduct formed between bis (O- ethylxanthato )nickel(II) and triphenylphosphine is reported. The nickel atom is five-coordinate in a distorted square-pyramidal geometry with a sulfur atom, from an asymmetrically coordinating xanthate ligand , in the apical position. Crystals are triclinic, space group Pī, a 10.265(4), b 14.718(5), c 8.818(4) Ǻ, α 100.77(3), β 92.16(4), γ 89.56(3)° with Z 2. The structure was refined by a least-squares method; R 0.068 for 3301 reflections with I ≥ 3.0σ(I).