The coordination ability of 4-amino-4H-1,2,4-triazole with Pt(II), both in solution and solid states, is elucidated by conventional and linear-polarized IR spectroscopy of oriented colloid suspensions in nematic host, 1 H-and 13 C-NMR, UV-Vis spectroscopy, mass spectrometry (ESI and FAB), TGV, and DSC methods. The interpretation of the spectroscopic characteristics of corresponding metal complexes is obtained by comparison with free 4-amino-4H-1,2, 4-triazole. In addition, quantum chemical calculations of the last compound are performed to obtain data for electronic structures and optical properties of the ligand, thus supporting the experimental elucidation. The evaluation of the cell viability on a panel of human tumor cell lines is made. The new Pt(II) complexes exerted cytotoxic effects in a concentration-dependent manner.