The interaction of conjugated polyelectrolyte, PPE-SO3-, with platinum(II) complexes, [Pt(tpy)(C CC6H4-CH2NMe3-4)](OTf)(2) (1) and [Pt(tpy) (C C-CH2NMe3)]- (OTf)(2) (2), has been studied by UV-vis, and steady-state and time-resolved emission spectroscopy. A unique FRET from PPE-SO3- to the aggregated complex 1 on the polymer chain with Pt center dot center dot center dot Pt interaction has been demonstrated, resulting in the growth of triplet metal-metal-to-ligand charge transfer ((MMLCT)-M-3) emission in the near-infrared (NIR) region. This two-component ensemble has been employed in a "proof-of-principle" concept for the sensitive and selective label-free detection of human serum albumin (HSA) by the emission spectral changes in the visible and in the NIR region. The spectral changes have been ascribed to the disassembly of the polymer-metal complex aggregates upon the binding of PPE-SO3- to HSA, which is rich in arginine residues and hydrophobic patches, leading to the decrease in FRET from PPE-SO3- to the aggregated platinum(II) complex. The ensemble is found to have high selectivity toward HSA over a number of polyelectrolytes, proteins and small amino acids. This has been suggested to be a result of the extra stabilization gained from the Pt center dot center dot center dot Pt and pi-pi interactions in addition to the electrostatic and hydrophobic interactions found in the polymer-metal complex aggregates.