4-Sila-3-platinacyclobutene was isolated from the reaction of Pt(SiHPh2)2(PMe3)2 with dimethyl acetylenedicarboxylate (DMAD) and characterized by X-ray crystallography. The formation pathway was found to involve gamma-Si-H bond activation of the 3-sila-1-propenylplatinum intermediate that is formed by the insertion of a DMAD into a Pt-Si bond of Pt(SiHPh2)2(PMe3)2.