The complex (pyPh₂PO)PtBr₄ (pyPh₂PO is 2-pyridyldiphenylphosphine oxide) has been synthesized by three different pathways, and its structure has been established by X-ray crystallography. C₁₇H₁₄Br₄NOPPt crystallizes in the space group P2₁/c (no. 14) with cell dimensions (at 140 K) of a = 13.696(7), b= 16.653(5), c = 17.612(7) Å, β = 92.23(4)°, Z = 8 and V = 3993(3) ų. The structure was refined by block-cascade least-squares to a conventional R value of 0.048 using 3647 significant data. The structure involves a six-coordinate platinum((IV) ion with the chelated ligand bound through its nitrogen and oxygen atoms. The two crystallography independent molecules in the asymmetric unit have very similar dimensions. To our knowledge this is the first reported structure of a chelating phosphine oxide. The PtOP angles within the rings are 114.4(6)° and 117.4(6)°.