The presented work, submitted as a paper, deals with the substitution reactions of mononuclear and dinuclear platinum(II) complexes of di‐2‐pyridylaminodiaquaplatinum(II), (Pt1); di‐2‐pyridylaminomethylbenzenediaquaplatinum(II), (Pt2); 1,2‐bis(di‐2‐pyridylaminomethyl)benzenetetraquaplatinum(II), (Pt3); 1,3‐bis(di‐2‐pyridylamino‐methyl)benzenetetraquaplatinum(II), (Pt4); and 1,4‐bis(di‐2‐pyridylaminomethyl)‐benzenetetraquaplatinum(II), (Pt5). These reactions were carried out on aqua complexes by three nucleophiles, viz., thiourea, N,N′‐dimethylthiourea, and N,N,N′N′‐tetramethylthiourea under pseudo–first‐order conditions as a function of nucleophile concentration and temperature by stopped‐flow and UV–visible spectrophotometric techniques. In addition, some DFT calculation was performed. The activation parameters support an associative substitution mechanism.