Platinum(II) complexes with 1,2,4-triazolo[1,5- a]pyrimidines of general formula trans-[PtCl 2(dmso)(L)], where L=1,2,4-triazolo[1,5- a]pyrimidine (tp), 5,7-dimethyl-1,2,4-triazolo[1,5- a]pyrimidine (dmtp), 5,7-diphenyl-1,2,4-triazolo[1,5- a]pyrimidine (dptp), 5,7-ditertbutyl-1,2,4-triazolo[1,5- a]pyrimidine (dbtp) have been prepared by direct reaction between cis-[PtCl 2(dmso) 2] and respective 1,2,4-triazolo[1,5- a]pyrimidine in molar ratio M:L=1:1. All new platinum(II) compounds were characterized by 1H, 13C, 15N, 195Pt NMR and IR. Significant 15N NMR upfield shifts (75–87 ppm) were observed for N(3) atom indicating this nitrogen atom as a coordination site. Crystal structure of trans-[PtCl 2(dmso)(dmtp)] ( 2) has been determinated. The molecular structure indicates that Pt(II) ion has the square-planar geometry with N(3) bonded dmtp, S-bonded dimethylsulfoxide and two trans chloride anions.