The electron-rich platinum(II) derivatives [Pt(R)2(DMSO)2] (R = Me, Ph) react with 2-vinylpyridine (L) to give the cyclometalated complexes [Pt(L–H)(R)(DMSO)] through C–H bond activation. Cyclometalation also occurs with [Pt(Me)(Cl)(DMSO)2]. From the starting compounds, a series of cyclometalated complexes was obtained and characterised by analytical and spectroscopic methods. The molecular structures of [Pt(L–H)(Me)(PPh3)] and [Pt(L–H)(Ph)(PCy3)] were solved by X-ray diffraction analysis, and the results unambiguously demonstrate cyclometalation of 2-vinylpyridine. The five-membered cyclometalated ring is particularly stable, likely due to partial electronic delocalisation.