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An Ir^III-Pt^II heterodimetallic complex [(ppy)₂Ir(dapz)PtCl₂]Cl (<b>4</b>), together with the corresponding monometallic complexes [(dapz)PtCl₂] (<b>2</b>) and [(ppy)₂Ir(dapz)]Cl (<b>3</b>) was designed and prepared, where dapz is 2,5-di(<i>N</i>-methyl-<i>N</i>′-(pyrid-2-yl)amino)pyrazine and ppy is 2-phenylpyridine, respectively. Single-crystal X-ray analysis was carried out for complex <b>4</b>, displaying the intermolecular Pt∙∙∙Pt and aromatic plane∙∙∙plane distances of 3.839 and 3.886 Å, respectively. The monometallic complex <b>2</b> exhibits a single emission maximum at 432 nm with a shorter excited-state lifetime (<i>τ</i>) of 6 ns, while complex <b>3</b> exhibits an emission band at 454 nm with a longer excited-state lifetime of 135 ns in CH₃CN (N₂-saturated) under ambient conditions. In contrast, the heterodimetallic complex <b>4</b> displays intriguing excitation wavelength-dependent dual singlet and triplet emissions. Theoretical calculations of the electronic structures and absorption spectra of these complexes were carried out to assist the interpretation of these experimental findings.