The nitrile complex trans-[PtCl4(EtCN)2] reacts with the aldoximes HONC(H)R [R=C(Ph)(O), Me, Ph] in CH2Cl2 to afford products of the addition of the aldoxime HON group across the nitrile CN triple bond, i.e. trans-[PtCl4{NHC(Et)ONC(H)R}2] (1–3). These compounds were characterized by elemental analyses, FAB MS, IR and 1H and 13C{1H} spectroscopies and X-ray structure determination has been performed for 1. In CHCl3 solution, 1–3 undergo the spontaneous imine ligand splitting to achieve the carboxamide complex trans-[PtCl4{NHC(Et)OH}2] and RCN thus giving the first example of a ligand-mediated dehydration of aldoximes. The carboxamide and RCN products are also formed upon treatment of trans-[PtCl4(EtCN)2] with 2 equiv. of HONC(H)R in CH2Cl2.