The synthesis and characterization of a polymer with pendant groups carrying a cis-platinum complex by the chemical modification route is discussed. Diethyloxomalonate functionalized polystyrene (DPS) is synthesized by the Friedel-Crafts acylation of polystyrene with diethyloxomalonate in the presence of SnCl4, by a batch-wise addition process. The reaction of DPS with cis-diaquo(trans-l,2-diaminocyclohexane)-platinum(II) results in the formation of a cis-platinum chelated polymer (PtDPS). Proton NMR and IR spectroscopies are used to confirm the transformation. The polymer synthesized is further characterized using thermogravimetric analysis (TGA) as well as UV and fluorescence spectroscopic techniques. PtDPS thus synthesized is further modified into a water-soluble polymer by another polymer modification reaction resulting in the introduction of thiobarbituric acid moieties.