The photophysical and luminescence quenching properties of a platinum(II) acetylide-based conjugated polyelectrolyte, Pt-p, which features carboxylic acid solubilizing groups are reported. The Pt-acetylide polymer is water soluble, and it exhibits phosphorescence from a triplet pi,pi* exciton based on the conjugated backbone. The phosphorescence from Pt-p is quenched by viologens with different charges (MV+, MV2+, and MV4+), and in each case the quenching is dominated by a dynamic (diffusional) mechanism. Comparison of the Stern-Volmer quenching properties of Pt-p with those of a structurally analogous fluorescent organic polyelectrolyte leads to the conclusion that the amplified quenching effect, which is commonly observed for fluorescent conjugated polyelectrolytes, is not important for the platinum acetylide phosphorescent conjugated polyelectrolyte.