Here we report five blue‐phosphorescent platinum bis‐phenylacetylide complexes with an investigation of their photophysical and electrochemical attributes. Three of the complexes (1–3) are of the general formula cis‐Pt(CNR)2(C≡CPh)2, in which CNR is a variably substituted isocyanide and C≡CPh is phenylacetylide. These isocyanide complexes serve as precursors for complexes of the general formula cis‐Pt(CNR)(ADC)(C≡CPh)2 (4 and 5), in which ADC is an acyclic diaminocarbene installed by amine nucleophilic addition to one of the isocyanides. All of the complexes exhibit deep blue phosphorescence with λmax ∼430 nm in poly(methyl methacrylate) (PMMA) thin films. Whereas isocyanide complexes 1–3 exhibit modest photoluminescence quantum yields (ΦPL), incorporation of one acyclic diaminocarbene ligand results in a three‐fold to 16‐fold increase in ΦPL while still maintaining an identical deep blue color profile. The rising of the photoluminescence quantum yield: This work describes a new design for blue‐phosphorescent platinum acetylide complexes, using strong σ‐donor acyclic diaminocarbene (ADC) auxiliary ligands. Conversion of one isocyanide in the precursor complex to and ADC, by nucleophilic addition of a secondary amine, engenders up to a 16‐fold increase in photoluminescence quantum yield.